I bought one last year from newegg. I have a gateway core 2 quad with a terabyte HD, 4GB memory and DL dvd burner. It came with Vista Home Premium. Only thing I didn't get that I wanted was bluetooth. I can get a dongle for $15, so it wasn't a deal breaker. Only issue I had with it, wasn't really computer related, they forgot the remote (media center). I called and got it a week later. I do believe I could have gotten the extended warranty with it.
Research the pc, research who you get it from also. I almost bought from another site until I started reading about things being sent and not received and the company basically saying "oh well." I've been buying from newegg for years now, so I knew I could trust them.
If you're quick and have time to spend to watch, there is a woot-off still going on. They usually throw on a few computers. Actually one on there right now.