This worked for me too. I'm a noob but found this quite straight forward.
Did it manually though, not using GFX String tool.
changed apple.boot to <string>arch=i386 PCIRootUID=1</string>
Got graphics card device id from 'About This Mac'... id was 06e4.
Duplicated an id string from the list within NVDANV50Hal.kext/ contents info.plist
then just changed the id to match my card.
New id string should look something like this: 0x06e410de&0xffe0ffff - P.S. no need to be bold text
then just repaired permissions with the latest mulitbeast.
Now running 10.6.7 on a G31M-ES2L v2.0 Core2Duo e6500 and an Asus GeForce 8400GS.
A million thanks Husky..
Now just need to sort out sleepenable.
Thanks to everyone on the TonyMac team and to all members. Great work!!