Your personal startup folder should be C:\Users\<user name>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup. The All Users startup folder should be C:\ProgramData\Microsoft\Windows\StartMenu\Programs\Startup. You can create the folders if they aren't there. Enable viewing of hidden folders to see them.
You can mouse into the All Users Startup folder by going to:
Start > All Programs, then right-click on Startup and selecting "Open".
This direct route should work for admins even if the "show hidden files and folders" setting isn't activated and the "C:\Program Data" directory is not visible.