Well ill let you in on a secret. You could have probably googled to find this but heres the fix. You buy a 2nd hard drive. Buy the upgrade version of vista. Unplug the hard drive with xp on it from your motherboard. You have to do this because vista will not install onto a second hard drive from within xp, it will bluescreen during install and nuke your xp drives bootldr. So you have a new hard drive plugged in only, throw in the vista install dvd. When it asks you to enter your vista key DONT DO IT leave the space blank and click next. Select the version of the upgrade you purchased and install it. You just new installed a 30 day trial of the os you purchased as an upgrade. THEN when vista starts, register it with your upgrade key, and voila you installed a 30 day trial of a full version and activated it with a upgrade key. Its that simple. Plug your xp drive back in and you will have to use f8 to decide what disk you will want to boot to after your motherboards bios screen. Default will be vista. You can change it in the bios. Im guessing you will use vista about 4 times before you find out its a joke