dell
I bought a refurb Dell XPS 1530 2.4 ghz, 3GB RAM, 160gb 7200rpm HDD, 256 8600GT nvidia card AND it has a Blu-Ray player & BURNER and it cost me under $1400. I know that's out of your range but you can certainly buy one of the new Dell Studio 15" new or an XPS 1530 refurb for under $1000.
(note: I have a Macbook & and iPhone too so please no calling me a Windows shill for the following )
As for Vista, if you are buying a new computer and not worried about hooking up a 5 year old printer or using 4 year old software on it you'd be a complete fool NOT to install Vista on your PC IMHO. I have Vista Business running on a Lenovo X61 tablet, & Vista Premium running on a XPS 420 desktop in addition to the XPS 1530 laptop and it runs great. In fact, I have never had a single crash, freeze up or need to reboot (other than for updates), not one time with three Vista computers running a total of about about 18 months worth of time. The Lenovo I picked up 9 months after Vista was released and the two others 11-16 months after Vista came out.
Yeah, there were problems at first with driver support that hit people who tried to install it on older machines or people who bought computers that met the minimum requirements, a real foul up by Microsoft to set the standards so low. However, if you're buying all new stuff or have relatively new equipment and you're going to have 2GB RAM minimum you're golden. If you have a 3 year old computer with 1GB of RAM or less and you've got even older peripherals attached to it then stay the hell away from Vista, but don't be scared off by all the advertisements you see. They just arent true anymore.