Try

Remove-PublicFolder -Identity "\Internet Newsgroups" -WhatIf

from the PowerShell. Does this say it will complete successfully? If so, run it again without -WhatIf, if not, copy the error generated and post here

-BBRazz

Running that command with -WhatIf displays as follows:
[PS] C:\Windows\System32>Remove-PublicFolder -Identity "\Internet Newsgroups" -W
hatIf
What if: Removing public folder "\Internet Newsgroups".
[PS] C:\Windows\System32>
Without - WhatIf:

[PS] C:\Windows\System32>Remove-PublicFolder -Identity "\Internet Newsgroups"
Confirm
Are you sure you want to perform this action?
Removing public folder "\Internet Newsgroups".
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help
(default is "Y"):y
Remove-PublicFolder : Cannot delete the object '\Internet Newsgroups'. Please m
ake sure that you specified the correct identity and that you have the correct
permissions to delete it.
At line:1 char:20
+ Remove-PublicFolder  <<<< -Identity "\Internet Newsgroups"
[PS] C:\Windows\System32>
Same error.
-F

if you use "Get-PublicFolderAdministrativePermission Identity "\Internet Newsgroups"  | fl" whats the output?

More infor on the CMDLET at http://technet.microsoft.com/en-us/library/bb124917.aspx

-BBRazz

[PS] C:\Windows\System32>Get-PublicFolderAdministrativePermission Identity "\Int
ernet Newsgroups"  | fl
Get-PublicFolderAdministrativePermission : A parameter cannot be found that mat
ches parameter name '\Internet Newsgroups'.
At line:1 char:41
+ Get-PublicFolderAdministrativePermission  <<<< Identity "\Internet Newsgroups
"  | fl
Is the command properly formatted, or is this an error?
-F

try

Get-PublicFolderAdministrativePermission -server servername -identity "\Internet Newsgroups" | fl

Check you can see that your admin user has "AllExtendedRights"

-BBRazz

It was missing a dash...

[PS] C:\Windows\System32>Get-PublicFolderAdministrativePermission -Identity "\In
ternet Newsgroups"  | fl
AccessRights    : {ViewInformationStore}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange View-Only Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {ViewInformationStore}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Public Folder Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {ViewInformationStore}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\SBS Mail Operators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {AdministerInformationStore}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Public Folder Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {ModifyPublicFolderACL}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Public Folder Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {ModifyPublicFolderQuotas}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Public Folder Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {ModifyPublicFolderAdminACL}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Public Folder Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {ModifyPublicFolderExpiry}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Public Folder Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {ModifyPublicFolderReplicaList}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Public Folder Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {ModifyPublicFolderDeletedItemRetention}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Public Folder Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {AllExtendedRights}
Deny            : False
InheritanceType : Descendents
User            : MYDOMAIN\Exchange Domain Servers
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {AllExtendedRights}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Servers
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {AllExtendedRights}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Domain Servers
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {AllExtendedRights}
Deny            : False
InheritanceType : All
User            : NT AUTHORITY\SYSTEM
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {AllExtendedRights}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Exchange Organization Administrators
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {AllExtendedRights}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Administrator
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {AllExtendedRights}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Enterprise Admins
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
AccessRights    : {AllExtendedRights}
Deny            : False
InheritanceType : All
User            : MYDOMAIN\Domain Admins
Identity        : \Internet Newsgroups
IsInherited     : True
IsValid         : True
ObjectState     : Unchanged
 

Try the suggestiong from the following EE post.

https://www.experts-exchange.com/questions/23370537/Unable-to-remove-Internet-Newsgroup-public-folder-which-prevents-uninstall-of-exchange.html

-BBRazz

Is this the only way? Would rather not hack it.
I opened ADSIEdit, and cannot even find the node anywhere in the tree.
-F

You could try adding your permissions again and setting yourself as OWNER

http://technet.microsoft.com/en-us/library/aa997986.aspx

-BBRazz

Tried that, still cannot delete. ADSI Edit may be the only way, but I cannot find the node to delete.
-F

Internet Newsgroups is a system group created by Exchange. I don't think you can delete it.

-M

Yeah, I think it's a legacy group. I was cleaning up the Public folders because when users click on them in Outlook, it would hang, then finally say it could not display the contents of the folder. Also, I have this critical alert once a day on the SBS Server:
OALGen encountered error 80004005 while cleaning the offline address list public folders under /o=MYDOMAIN/cn=addrlists/cn=oabs/cn=Default Offline Address List. Please make sure the public folder store is mounted and replicas exist of the offline address list folders. No offline address lists have been generated. Please check the event log for more information.
- Default Offline Address List
I think it may be related.
-F

Have you done what the error says, and replicated the OAB folders to the new server? All OAB folders should have at least one replica listed.

With regards to Internet newsgroups, I wonder how it got there? Did you use some kind of script to replicate your public folders?

Do your users get a hang from Outlook when they use any public folder?

-M

Yes, they were getting a hang when using any public folder.
I used the migration Wizard to go from SBS 2003 to SBS 2007. I remember when I got to the part to migrate the Public Folders, I did not want to bring over any of the folders because it was all old stuff, and I wanted to use SharePoint doc libraries for that type of stuff going forward. I think that may be the source of the problem.
So I guess I have not replicated the OAB folders to the new server?
The other related critical error in the event log is this:
OALGen encountered error 80004005 (internal ID 50101ee) accessing the public folder store while generating the offline address list for address list '/'.
- Default Offline Address List  
-F

Sounds like you didn't replicate the system folders. That would cause a lot of problems, particularly if the Outlook users are on 2003. I am surprised the migration wizard didn't do that for you. OAB puts content in the OAB system folders. If they aren't there, then it cannot.

How old is the migration? Is the old server still available?

-M

The migration is 2 weeks old. The old server is available but we ran the decommission steps from the migration wizard. I'm not sure what gets left behind after that.
What do you mean by system folders?
-F

Do I need to do this to reset system folders?
http://technet.microsoft.com/en-us/library/bb331972.aspx 

I do see System folders though using the Public Folder Management Console.
(see attached screenshot)
-F

publicfolders.jpg

If you do get-publicfolderstatistics, do those system folders actually have any content in them?

-M

Looks like zero counts in all.

[PS] C:\Windows\System32>get-publicfolderstatistics

Name                                     ItemCount               LastAccessTime
----                                     ---------               --------------
EX:/o=MYDOMAIN/ou=Exchange Administrativ 0                  1/9/2009 1:00:01 AM
e Group (FYDIBOHF23SPDLT)
EX:/o=MYDOMAIN/ou=Exchange Administrativ 0                 1/8/2009 10:10:58 PM
e Group (FYDIBOHF23SPDLT)
globalevents                             0                 1/3/2009 12:22:58 PM
internal                                 0                 1/3/2009 12:22:58 PM
OWAScratchPad{60C5ABB1-524A-4754-81AF-01 0                 1/7/2009 12:05:11 PM
FD663A4C85}
StoreEvents{60C5ABB1-524A-4754-81AF-01FD 0                 1/7/2009 12:05:11 PM
663A4C85}

Was that the complete output?
It should be longer than that. That would explain the errors. You don't have the OAB folders in there at all.

As you can see the folders through the management tool, right click on each one and ensure that there is at least one server listed on the replication tab. If not, add the server.

-M

That was the complete output.
There is a server listed in the replication tab, but I noticed some settings look truncated on the 'Exchange General' tab. See the error below. The blurred out areas are obviousely our domain name.
Can this be the problem?
-F
publicfolders2.jpg

OK, I mail disabled them and restarted the store.
The replication server setting for these system folders was pointing to the old 2003 server, so I updated it to point to the 2007 server.
There are other system folders that are set to Mail Enabled:
SCHEDULE+FREE BUSY
schema-root
StoreEvents

Should they also be set to Mail Disabled?

-F

Yes, all three of those. I can't find a single system folder that is mail enabled on my reference system - although I wouldn't change any others than those already mentioned.

-M

I'll do those too. I'm not sure why the replication settings on many of these are pointing to the old 2003 exchange server. Even when I open the Select Public Folder Database dialog to replace it with the 2007 server, it still appears as available to select in the list. It must still be in AD. There's a First Storage Group which points to the old server, and a Second Storage Group which points to the new server.

Replication is a bit odd. Things can still appear even after the server has gone.
Go through the folders and ensure that the new server only is listed everywhere. It will take a while to catch up before things start to behave.

-M

Thanks a million for your help...you truly are an expert in this area. You solved my problem by having me reset properties on the System folders. I no longer need to remove the Internet Newsgroups Public folder, because it does not hang on Outlook clients anymore.
-F