Castout - to understand why you must be an admin to tweak services is imagine yourself as a user that doesn't know what the hell they are doing and you start turning off critical stuff.....
jk! I couldn't resist!
It is to protect your system from exactly what you describe above. In your case however, it was a good learning experience since you now know where to find your services.
-S
PS. If you want to learn more about services and programs that run on boot up on your system, pull up a run box (hold the key down with the MS windows logo and then push 'R') and type msconfig in the run box. That will allow you to disable and re-enable items at will without it becoming permanent. That way you can selectively start up items every time you boot. It will teach you a lot about what things are needed at boot time. The great thing about it is, you can always easily 'undo' whatever thing you did.
PPS. To modify start up programs with msconfig, as you may have guessed, only an administrator can do that.