Windows Vista Beta: How to dual-boot Windows XP and Windows Vista - Lifehacker

If you need to get out of Vista, and get back to XP, try this:

Windows Vista Beta: How to dual-boot Windows XP and Windows Vista - Lifehacker:

"type FIXBOOT followed by FIXMBR "

I was unable to modify the boot order and defaults from within XP. Vista uses a new system. So, if you wish to remove Vista, be very careful. Don't just blunder in from XP and remove the partition... The technique that I used was to boot off the XP CD and enter a recovery console. Then, after logging is as administrator, type FIXBOOT followed by FIXMBR and exit to reboot. It goes without saying that you should be sure that you have a backup before doing this. You do, don't you? This will get you back to your original XP boot process.