$1000 because of the warranty, if the right customer came around I could probably get $1200-$1300.
I know this is nowhere near what it cost when new, but you have to consider that it is used and that prices have come down since it was purchased.
Im workin in pounds and i wass hopin to get £500+ for it... if its $600-800 then thats nowhere near that. The warranty alone is worth about £150-200.... And with the monitor i would definatly expect to get over £500...
To some people warranty isn't worth all that much, remember that you can't value things like that. I'd say the hardware + windows is worth maybe around $850 new from retail, so yours used is maybe around $750.