as a computer technician who used to work for Fry's, I know for a fact it all depended on the laptop you were trying to downgrade. We had sales people all the time promise that we could downgrade the laptop to xp for the simple cost of the operating system.
Time and Time again, we ran into the problem of not finding all the drivers for the components in the laptop. I got SOME of them to take the downgrade but that was only after trial and error with 3rd party drivers and generic issues. It caused conflicts with other drivers and never really functioned properly. The laptops were unstable as hell, period.
The only computer I was able to sucessfully install XP on that still had vista was an older Sony Viao, but it only took XP because it was an older computer with older xp compatible components...
Oh, and a store does not HAVE to downgrade you. And you can go ahead and find another place that says they will. But when you have to go back and get it fixed time after time. You will wish you had just listened to the first store in the first place.
Do what I did, Buy a Macbook
