Are you sure that you are renaming the proper startup folder. There are most likely a few if you are using windows xp. If you Rename the one under "Documents and settings\Your Profile\Start Menu\Programs" Then it should work. Have you also tried just right clicking the folder in the start menu directly and clicking "rename"? Good luck.
I am using XP Home edition. For some reason the folder "StartUp" has changed names. If I Explore on the C: drive I see "Start Menu, Programs, Programs". It should be "Start Menu, Programs, StartUp". If I rename the Programs folder back to StartUp, I then find that my directory looks like "Start Menu, StartUp, StartUp". Not sure what is happening. How can I change the directory structure back to "Start Menu, Programs, StartUp"?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic