I had a case of a drive filling up with nothing significant to delete and of course everybody needed everything. I decided to run disk cleanup to see if I could at least compress old files.
I entered: cleanmgr
I was rewarded with a file not found message.
It turns out the Desktop Cleanup utility is not a default install with 2008. There are two ways you can install it.
The first would be to install the Desktop Experience feature which adds other missing desktop features. The problem with this approach is the system will need a reboot to finish the install.
The second would be to simply copy a couple files to appropriate locations.
Look in the winsxs folder for the following:
Cleanmgr.exe to %systemroot%\System32
Cleanmgr.exe.mui to %systemroot%\System32\en-US
Now cleanmgr will function as expected.
This technote helped with the second option.