I had a Dell XPS 400 from February 2006 and it worked pretty good for me and still would if I didn't want to play some demanding games like FSX. (It also just died when I cleaned it after removing a HDD to put in my new build). I upgraded it to 2 GB of RAM and replaced my old GT 6600 with a GTX 8600 (my 380 watt psu couldn't handle any higher GC and replacing it PSU was out of the question).
Honestly, for less than $1000 you should be able to find/build a pretty decent editing rig. You can get a good C2D CPU for under $200, 4GB RAM for around $100, a good MoBo for ~$200, Graphics for ~$150-200, 1TB HDD for ~$180-200, Opitcal Drive for < $80, and a case for ~$80.
Some other PC manufactuers also have some competent PCs just under or a little over $1000. Just avoid Alienware...
My High end build with a C2D 8500, 4GB Corsair RAM, EVGA GTX 260, Thermaltake Armor Full Tower, EVGA 780i SLI, Thermaltake 750Wt PSU, Lightscribe CD/DVD burner, Seagate 500 GB HDD, 22' Acer display, and Creative Sound Blaster Extreme Gamer ran me about ~$1600 before some $300 in rebates and such.