pastafreak, what that program deleted was ALL your temporary files, which can be a lot.
Original question was about Temporary Internet Files which are a slightly different thing.
Every time you install a new progam it may put files a folder called "Temp", and after the install it just leaves them there.
Even if you uninstall the program it probably leaves files in the Temp folder.
After two years then the Temp folder can be quite big.
I have just done a clean install of Windows, and my temp folder is already 40Mb.