Compaq Presario? I used to work for HP and I would agree with dinowuff but replace Best Buy with HP and repair tech with tech support! If you rang HP they'd likely tell you the same thing.

I wouldn't worry at all about replacing Vista with XP - if anything, you're likely to find drivers more easily if you've got HP installed. I was amazed when I first installed Vista, that out of 15GB of bloat, there wasn't even basic support for a USB key for instance - that only came with one of the first updates!

I've replaced operating systems on several laptops without ever encountering a problem. My old laptop came with Windows 98 - I first of all put Me on, then decided to try a stripped down version of XP (XP lite). That ran fine. I then added Suse 9, as a dual boot, which again worked very well. When I got my new laptop, it came with XP Media Centre Edition but promised a free upgrade to Vista Home premium, which I took advantage of in due course. Now obviously it was going to come equipped for Vista, bought in December 2006 and offering the upgrade, but the point is I've never had a problem switching operating systems. In fact, I never used the "upgrade" CD. I had bought an OEM version of Vista Home Premium for this PC which I installed onto the laptop whilst waiting for the upgrade to arrive. In due course it ran out of activation time, and when I got the upgrade I tried simply putting in the key I was given. I was surprised and pleased when it activated Vista! Now I know I can reinstall (in fact I have done) without problems which would have existed if I'd been forced to upgrade from XP.