There are no good games that can fit on a 30gb HDD, especially some old slow POS one. In fact, you could build an excellent system, throw your old HDD in it, and get terrible, terrible performance with your HD as the bottleneck.
Build yourself a new computer. If your going budget, get your self a bargain case and mobo, i5 2500k, 560ti, 8gb cheap ram, bargain PSU, and at LEAST a 1tb HDD. KABAM done deal.