Well... I could point out some PC distributors with more flexibility, or go into linux dualboots. And mention that even in brick and mortar stores, you can easily find a new computer without Vista. It's called a Mac. Surely you've heard of Apple?
Sorry, had to get that smart-aleck out of my system.
I know what you meant. And considering where the bulk of the market is, Vista capability may be an unfortunate necessity.
Personally, I have no interest in Vista. I may go out of my way to avoid migrating to it. But I do want to be helpful, so I'm doing some google searches online. Unfortunately, my searchs didn't turn up much. But you may want to try window's vista's compatibility mode. It allows you to select specific versions, including Windows XP, Service Pack 2.
http://cws.internet.com/article/3645-.htm
It's described down at the bottom of the article. I'm not confident it will help, but it is very quick to try out.
http://www.worldstart.com/tips/tips.php/3817