[Scorched Earth]

Im looking to buy a new computer because my current one is soo outdated. This comp is....1.7ghz, 512 mb ram, 80 gigs harddrive space..sounds ok but my vid card is also a NVIDIA RIVA TNT2 (no "pixel shading" so all these new games are way too advanced for my comp. a combination obsolete parts and overload of unkillable viruses has led me to decide to buy a new comp. Im looking for a computer more directed towards gaming but also below $1300. i found the Gateway 830 Media Center Desktop 840GM ($1050) , and a few other gateways very similar to that but $850. Im not sure if i would rather buy parts, which is most likely cheaper but with the chance of me screwing up lots of stuff and ending up paying more, or to buy a preconstructed. Any suggestions for what to do and good sites to look into this on? Thanks.