Read Only C:drive

No, this is normal behavior...   The explorer won't really let to set the read only property on directories (although it appears to support that feature)

As ofr the other problems associated with your ASP.... that's an "Operation Failed"... not a permissions problem.   The ODBC driver for Access requires a system-level TEMP environmental variable to be set.   Do a right-click on My Computer, System, Advanced Tab, Environmental Variables button, in the System section, make sure you've got both TMP and TEMP set to some valid directory.

Both TMP and TEMP set to a valid dir.
All other ASP pages that get data from the Access file (.mdb) work apart from the ones that submit an entry to the Access database, which leads me to think that it may be some sort of permissions thing.
Error:
Microsoft OLE DB Provider for ODBC Drivers (0x80004005)
[Microsoft][ODBC Microsoft Access Driver] Cannot update. Database or object is read-only.
/intranew/addtomsgboard.asp, line 42

Hummm.... OK

Check the permissions on the *.mdb file itself... see if the IIS user account has read/write permissions.

>>This means that some files are read-only and some are not
not true...

folders cannot have the read only attribute, this is a file attribute and cannot be set on a folder at all.... see the links below:

http://support.microsoft.com/default.aspx?scid=kb;en-us;326549
http://www.annoyances.org/exec/forum/winxp/1065399208
http://www.experts-exchange.com/Operating_Systems/Q_20941466.html

so bascially, the fact that they are getting access denied has nothing to do with that "read only" thing you see on the folder, since it basically means nothing,,,,, you need to check their NTFS permissions (on the security tab) of both the folder/drive and file itself and make sure they have the proper permissions.

below is a quote from the first MS link:
"Unlike the Read-only attribute for a file, the Read-only attribute for a folder is typically ignored by Windows, Windows components and accessories, and other programs."

Thanks TheClickMaster

The PC name had been changed since IIS was installed and the IUSR under the 'Directory Security' tab>Edit was showing the old PC name.

Cheers

The actual name of the IUSR_ account isn't important...   so don't worry about that.

Well changing it fixed my problem so obviously is fairly important

Hummm... a rather doubt that.  Not that I'm trying to argue with you... :)

The name of the IUSR_* account can be safely renamed to anything you want.  It doesn't change the permissions that are assigned to files/folders with that account.  Likewise, renaming the machine won't change the permissions assigned to that user account.

Are you saying that you had both a IUSR_* under the old name and another IUSR_* under the new name?

No, IIS was installed prior to the name change of the PC.
When this problem occured (post PC name change) the IUSR_* name was 'IUSR_OLDPCNAME'. So I changed this, by clicking on [Browse] > [Advanced...] > [Find Now] and selecting the PC user account from the list (PCNAME\USERNAME), then clicked [OK] > [OK].
I must admit, I'm not too sure how this works or what it has done, but it has fixed the problem. Maybe you can shed some light if you can follow my explanation.