My PC is a Windows 7 64 bit, with an Nvidia GeForce460 and a Radeon X800GTO
Radeons that old don't have openCL support, so they won't work, you'll need at least a HD4xxx or higher.
for your GTX460 you only need to install the CUDAToolkit (and recent drivers of course, but i bet you already have those installed).
you can then use any of the available gpu-miners, be it OpenCL, like poclbm
, or Diablos javaminer
, or CUDA, like the one from puddinpop
if you don't want to fiddle with the commandline, there's also a GUI-miner
, that (afaik) supports poclbm and puddinpops.