to prevent corruption of other programs, it needs to be uninstalled correctly. You could accidently disable a program your computer needs if you just dump the file, as some software uses shared data...
C:\Documents and Settings\All Users\Start Menu\Program\Startup
C:\Windows\Tasks
C:\Documents and Settings\username\StartMenu\Programs\Startup
C:\Users\username\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup