1. Trust the maker supplied uninstaller. However, realise this doesn't uninstall things added later by the program. You've got to do that yourself.
2. With Windows Explorer.
c:\windows\temp and Temporary Internet files spring to mind, but they can be cleared with the Disk Cleanup Wizard and/or IE Tools>Internet Options. And then we have files with names starting with a ~ (mostly temp-files) or with a .tmp extension (temp files by convention) that can be everywhere or autobackup's of MS Word. And some older programs might use c:\temp or c:\tmp folders.
Also note there's no good definition of a temp file. It's up to you if you think your IRS-data of 1998 or a letter you wrote in 2000 or a mp3-file you don't like any more temporary enough to delete by now or want to keep them forever. Or, maybe more apt, a bitmap of a scan you did yesterday and have printed already.
Hope this helps.
How to make sure that any programs uninstall completely in the computer?
how to find all the temp. files in the computer?
thanks for your answers!!