To move the WSUS Server update files to a separate drive I recommend reading the following:
Specifying Where to Store Updates
Managing WSUS from the Command Line
So I'm going to move my WSUS updates to a 500GB drive mounted as E:
Open CMD prompt and cd C:\Program Files\Update Services\Tools
run wsusutil.exe movecontent E:\ E:\wsus.log
and wait until it has completed the move.
Now the WSUS updates are now on the E Drive.
WSUS CMD TOOL |