First you should try and identify what process is holding those files in TEMP. You can use a command line tool like "handle.exe" from
http://www.sysinternals.com/utilities/handle.html
(they have many other great tools too, all free). This is a DOS command line tool. Then having identified the process that owns the files the next step will be to figure out what that process does, and you can google for the process name if nothing else which will give you some clues.
Do not delete files in TEMP without knowing who or what they are doing there. By the same token, it is a good idea to keep a close eye on TEMP from a security and system admin perspective.