Nvidia put a stop to bios flashing to Geforce series after the 6xxx cards and also stopped the usage of standard Geforce drivers for the Quadro's after the FX5xxx series ( like FX5950 Ultra n such ).
Unless u need the power that FX5600 offers, sell it and get an older Pci or Pci-X1 quadro and an 8800GTX ( then build a 2nd PC with the spare cash from selling the FX5600 ).
From what I've read that thing is damn near as fast as an 8800GTX but with 2x the memory. So I have nfc why you'd have any problems gaming on it in the first place. One guy said he did WoW maxxed out at 1280x1024 and got 130 fps easy.
OMFG !!! the Quadro FX 5600 does 32x FSAA all by itself @_@.