When programs are installed they install registry settings
if a part of the program is needed to start when windows
starts. I would be careful playing with this as it may
affect some programs and Windows itself.
The safest way to make changes is to use msconfig. This
allows a user to tick or untick start up keys without
having to delete them.
Click Start-run. Type msconfig and hit enter. Go to the
Startup tab. There you will see a list of programs that
start with Windows. Untick the ones you dont want to
start. If later you do need it just go back and retick the
item. Cheers.