I think there's a small language barrier here. I think Arclight, when he says how big is your CPU, he means how fast is it? i.e. megahertz. Is it a Pentium 2, 3, 4? 500mhz, more?, less?...
As far as a new video card, how much money can you spend?
$50?
Get the Geforce 2 MX400 64MB
$90?
Get the Geforce 2 TI 64MB
$160?
Get the Geforce 3 TI 64MB