Ok, here's what you do (the steps may not be 100% right but should be close enough to figure out):
#1. First things first, do a system restore point in case it doesn't work so you can revert back. Windows probably will do this for you anyway, but to be safe, do it manually.
#2. Download the forceware drivers
#3. Run the setup and "try to install them". I think at this point you reboot.
#4. The old drivers will still be in. Go to your videocard hardware driver details page (I think you can get here through the screen properties or the device manager screen) and select update driver.
#5. Windows will ask you whether you wan to install a new driver automatically or manually. CHOOSE MANUALLLY (i.e. a specific location)
#6. Click on DON'T SEARCH. I will choose the driver to install.
#7. You should see a list with the current driver you have. Choose "have disk"
#8. Browse to your system particion letter (C: usually) and look for a folder that should now have been created by the setup- an NVIDIA folder
#9. Choose the Win2kXP folder
#10. Choose the 53.03 folder
#11. Choose the nv4_disp.inf file
#12. You should now get a list of all the Nvidia chips. CHOOSE CAREFULLY. If you have the 5600 DON'T choose the 5700. Also don't pick the 5600 ultra. Pick the 5600.
#13. Do the usual ok ok ,whatever. If windows complains that the drivers are not signed/WHQL certified, just force it to continue anyway.
#14. I think after all this, you will have to reboot.
#15. Verify your properties. Click on settings on the desktop, click on advance. You should get the new nvidia driver pane to the left, click different fields, click on the first topmost "Geforce 5600 FX" category to check the driver version.
#16. The DLL's should display something like "Version 18.104.22.16803" The last 5303 is the 53.03 drivers. Do this just to verify you got the new stuff.
#17. Enjoy ! :-)