Probably not, but there is an agp version of the Radeon HD 3850 available.
@doug237: a GeForce 8 only makes sense, if you got a pretty recent system with a dual core processor (e.g. a Core 2 Duo or Athlon64 X2) and preferably DDR2 RAM. However, you probably got SDRAM (two types earlier). That will be a huge bottleneck, just like the processor. I think it is way better to keep your system as it was and use it as your working pc. To be able to play the most recent games, you need to buy a new system.

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