In the registry, under "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall" are all the entries on the "Add/Remove Programs" list. I've seen lots of websites saying to delete any keys here that you want to remove from the "Add/Remove Programs" list but I've found that some installations still keep there info in "Add/Remove Programs" even if you delete this (therefore making it impossible to uninstall the application).
The way I found was to add a DWORD value to each of the keys you want "hidden":
That way, if you want to uninstall the program at a later date, you just delete that DWORD and boom, it's back on the "Add/Remove Programs" list.
Now, how many of you people knew about this registry value?
Edit: 50 odd views and only 2 votes? C'mon people.