When running my graphics card Nvidia 8200 will only use 1 cpu of my athlon 62 x2 5400 2.8ghz. When I disabled the driver, it would use both processors but with no desktop effects, etc. I noticed this mostly with 2d applications when they would slow down a lot, vba and several wine apps.
Running 64 bit intrepid
athlon 64 x2 5400 2.8