Assuming you have a conventional "Upgrade Version" of Windows Vista,
you need to be at your Windows XP desktop, then insert the Vista DVD
in your DVD drive to upgrade.

Hi - guys i have been trying to upgrade from WinXP to Ultimate. My system
passed the compatibilty check with the message "There are no known system
issues preventing you from upgrading to Windows Vista."
Every time i try to upgrade I receive the following messages "compliance
check disabled" and "upgrade compliance check could not be performed" and the
'upgrade' option is greyed-out only the 'install' option is available.
My winxp is completely updated with latest ms patches so am not sure why. I
want to upgrade as i don't want to lose my existing settings/data/sofware etc.
anyone know why?

You might want to just get a Mac and install it that way. Apple's
hardware is much better quality and more compatible with Windows than
Wintel or Winamd hardware.

Prices for Macs are now about the same as PCs, starting around $500.

http://store.apple.com/1-800-MY-APPLE/WebObjects/AppleStore

the special deals are here:

http://snipurl.com/1rhuq

All your monitors, mice, keyboards, printers will work fine with a Mac
since Apple spends a lot more time than Microsoft making sure everything
"works".

It's a good direction to go if you want to have a better computer.

Try posting hardware specs here.
Like how much RAM, CPU, Graphics do you have?
Nobody can help you if you don't tell people what you have!