Define "quite large"?
There are no documented maintenance procedures for the file.
If it's genuinely "large", that could indicate one of two things:
[a] a lifetime history of updates on a system, or
[b] defective behavior in the AU system.
But, if you're out of space on your C: drive, there's a dozen other places
you should be looking to recover space than this one file.
--
Lawrence Garvin, M.S., MCTS, MCP
Independent WSUS Evangelist
MVP-Software Distribution (2005-2007)
Everything you need for WSUS is at
http://technet2.microsoft.com/windowsserver/en/technologies/featured/wsus/default.mspx
And, almost everything else is at
http://wsusinfo.onsitechsolutions.com
....