Syncing from XServe to MacBook Pro

First off, it's our head of school's computer, making it more of an issue. The computer is a MacBook Pro, there's a mobile home directory on our OD server, both running 10.5 client/server. I got a call saying he's out of memory. I check the computer, and there's 0K available on Macintosh HD. I clear up some space... a few minutes later, I see that it starts trying to sync again, and I watch the available space fall. Get Info tells me that Macintosh HD is using 238GB/238GB. If I do a Get Info on Applications, Library, System, Users, bin, sbin, private, usr folders, it maybe comes out to be a total of 50GB. Definitely no more than 100GB. Does any one know where temporary files from a sync might sit?