i got a compaq presario too, but a s6010v. i got it 2 years ago for only 299. bomb ass deal, 2.5ghz, 80gb, but 256mb ram.. dawwwg, don't spend 600 bucks on a used comp from a pawn store!! you can EASILY find one for about 400-600 that's HELLA better and much more decent than mine at any computer store..
check the sunday newspaper ads or online.. circuit city, best buy, fry's electronics, compusa, office depot/max...... you get the point. look around (not at a pawn store), they're CHEAP and worth it!!!