I think it is more than 350. Windows 7 Ultimate is around $150 dollars alone. I would say that you could probably get around $550-$600 for it, but idk, the 3 yrs. old will be a major turn-off for people, no matter how good the system is. Also, I do not recommend this selling via eBay, tried that a few months ago, and they will not buy any used electronic unless it is 200% below retail.
Hope this helped.