I had to replace my laptop a couple of months ago, and was frustrated with the options available at Best Buy. I ended up purchasing a used Dell Latitude because I didn't want to deal with the complications of Vista, and knew that I needed at least a gig of RAM, really 2 gigs, to make a PC work with Vista.
But I didn't need Vista - I needed something for internet research and blogging.
So I bought a used Dell Latitude, and put my old Windows XP license on it.
Vista comes preloaded on computers with 512 Mb of RAM, which means they won't work - which is just about the stupidest thing you can do if you're selling computers with 512 Mb of RAM.
Well, Dell agrees with me.