The only particles that render via software are the cloud and blobby surface (off the top of my head, there may be another one) the others need be rendered by hardware, as you've got a gforce card then that might be the problem, if your rendering using the right engine), as the gforce cards are not qualified by autodesk (although my 7900 GTX renderes them fine).
Another solution might be is to use mental ray, I think that in 8.5 it was introduced that mental ray can render previously hardware only particles, but I'm not too sure if it was 8.5 or 2008 where that was introduced (getting old and cant remember all the version changes!)
"No pressure, no diamonds" Thomas Carlyle