8800GT was a pretty good card when you bought it, but times have moved on and there are faster even more reasonable price cards now, but this is expected of computers.
If you were willing to look at AMD then I'd probably suggest trying a computer with their new integrated graphics processor, it apparently performs really well, and is very good at video decoding if you set it up, so you can tie it together with cheapish CPU and not have to worry about demanding tasks. The combination makes a strong cheap platform.
Unfortunately, Intel's counterpart graphics chipset has significant performance woes, even Intel have admitted it has problems. So if you want an Intel platform I'd highly suggest getting a cheap discrete graphics card like the nVidia 8400 or the ATi 3450