Ok sounds like it's a pretty new computer, what OS are you running. I've noticed alot that stuttering in games on fast machines can be a result of DMA not being enabled on your hard drive. So make sure DMA is enabled first off, I don't see how a 1.2GHZ machine with a GF2 Ultra could ever stutter in Half-Life, so if it's not DMA I'd have to say you should play around with some different drivers.