I was helping another member regain space on his hard drive. After doing disc cleanup, many temp files remained, per the excellent software windirstat
WinDirStat - Windows Directory Statistics
Further analysis revealed that it was his temporary files (20gb). With the help of Brinks excellent tutorial (Temporary Files - Temp Folder - Page 3 - Vista Forums
The 20gb were deleted.
I checked my own computer and realized that in spite of monthly maintenance, including clean disc (all files and system files), I had 3gb of temp files, which I was able to delete.
Place this great tutorial
resouce in your favorites or bookmarks and use the %temp% command once a month. The first time you try you will be amazed.
This great tutorial is equally appropriate for Windows 7