I have a Elsa Erazor ( 32 mb Geforce 256 DDR ) modifed to a Quadro using the information
Here . The Quadro modification I use is not switchable between Gefore and Quadro modes. The information provided by KILLorBE allows you to do this. I personally find stability is better when not using the switch.
The Quadro is Nvida's professional graphic chipset and converting the geforce to display as this card gives improvements details of which can be found with the information on doing the modification.
I would however suggest that you improve the cooling of the card and relocate the power source for the fan if this is on the Geforce card as they draw a lot of power through the AGP slot and this only adds to the problem.
I use Elsa cards as they are good quality and dont seem to mind a high FSB.. but this is just my personal opinion