I'd get a Windows 7 PC, Intel i5 or i7 Processor, 4 gb RAM, 15.6" display, 500gb 7200rpm HDD, DVDRW, 1gb dedicated (not shared) Video RAM, 6cell battery.
Cost about 850bucks. http://www.newegg.com/Product/Product.aspx?Item=N82E16834220864
Less still if you go i3 CPU/...