I got a laptop a few months ago and I dont like Vista. In order to not void the warranty by overwriting xp over it I wanted to install xp on an external hard drive and run it from there. I made a partition with xp on the hard drive but after the computer restarted to begin installation a blue screen came up with letters and numbers and thats where the installation stops. For my lack of time at that moment I thought I would just return it back to Vista and mess around with it later, so I erased the xp partition off the hard drive. Now when i turn the computer on, it wants to boot xp from the hard drive and a black screen comes up saying something along the lines of, "The disk is inconsistent or corrupt"

How do I change it back to boot Vista?