Start
here. Add 1905FP monitor for $50. Get another 512MB RAM for $40 or less, DVD burner for $25, 160GB HDD for $30 if you need more capacity, and a $50 DVI video card. Better than the Sony descktop you posted.
Or, hurry up and order
Dell 700m laptop for $750 and save $250 for a
19" LCD.