I figured I'd throw this in the off-topic section since it's technically an XP OS I'm dealing with... My laptop runs XP sp3 Media Center Edition. I was messing with an iso from my dad's XP Professional disc, mounted it, and tested to see if I could boot to the setup fine. It did, but this wasn't the computer it was intended for, so I stopped and have resumed everyday business on MCE.
I've unmounted the iso, but now every time I boot up, I get a black screen asking if I want to boot from MCE or the Pro setup. It's defaulted to Pro Setup & chooses that automatically after a few seconds. Just, really annoying. I don't know how to get rid of this setup option now... =/
(I've since learned that testing should only really be done virtually, and have since learned how.