freeing up space on 2008 R2 server

40 GB is not really enough space for any modern Server or Workstation operating system.

I suggest you run Disk Cleanup and select most of the options presented for deletion. You may need to install Disk Cleanup from Desktop Experience on your server.

When Disk Cleanup comes up, there is a button to clean up system files. Click on that and it will run again to present the items for cleanup.

Disk Cleanup is the Microsoft tool and is safe to use.

You might wish to make plans to add more disk space to your server.

thanks, Is their anything else that can be cleaned up, ie(updates)

dism /online /cleanup-image /spsuperseded /hidesp
or
dism /online /cleanup-image /spsuperseded

Dism.exe /online /Cleanup-Image /StartComponentCleanup   (run monthly as a scheduled task)
An in-depth cleanup but you can't uninstall and update after doing this
Dism.exe /online /Cleanup-Image /StartComponentCleanup /ResetBase

if you don't want to add the desktop experience (not supported) Server 2008R2

Copy C:\Windows\winsxs\amd64_microsoft-windows-cleanmgr_31bf3856ad364e35_6.1.7600.16385_none_c9392808773cd7da\cleanmgr.exe  %systemroot%\System32
copy  C:\Windows\winsxs\amd64_microsoft-windows-cleanmgr.resources_31bf3856ad364e35_6.1.7600.16385_en-us_b9cb6194b257cc63\cleanmgr.exe.mui %systemroot%\System32\en-US 

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http://blogs.technet.com/b/askpfeplat/archive/2014/05/13/how-to-clean-up-the-winsxs-directory-and-free-up-disk-space-on-windows-server-2008-r2-with-new-update.aspx
https://technet.microsoft.com/en-us/library/ff630161

Server 2008 R2 sp2, should I download http://support.microsoft.com/kb/2852386 and use desktop experience, so that I can cleanup winsxs folder?
it's 18.2 GB size

Yes, you should get Desktop Experience so you can use Disk Cleanup.

Disk Cleanup for Server 2008 will not much reduce Winsxs (same issue in Windows 7). Winsxs is a necessary folder for Windows to operate.  Do not manually delete anything here.

Look in your own folders for temporary or other files you might delete.

Mostly however, you do not have enough disk space.

Rindi, I am thinking that on folders within Dowloaad folder that are over 2 months old, that I could  delete those folders as an initial cleanup start. This is my dhcp dc server so I have to wait until all users are settled in, prior to installing or rebooting my dhcp dc server.

Do you mean the \SoftwareDistribution\Downloads folder? You can delete all the files in there immediately, unless of course there are still updates pending, as we've just had patch Tuesday. This doesn't have any influence on the server's function as a DHCP server.

You can check with TreeSize application folder size used and delete wanted folder. it gives clear view of folder size. Then you can delete. Be sure before any folder that not affect your server.

I have used treesize on other servers.
yes, \SoftwareDistribution\Downloads folder, I deleted folders prior to 2015, which gave me back 4gb space.
Not sure If I need to install desktop experience and but I will probably will, after I download http://support.microsoft.com/kb/2852386 for future cleanup.

You can get the cleanup wizard via the method ve3ofa expalined in his comment, or by adding the desktop experience. I would add that now, as it can reclaim quite a lot of space.