This is the simplest method to enable your graphics card. It was introduced in Chameleon 2.0, and is probably the most widely used method right now. Edit your com.apple.Boot.plist which is located in /Extra to add the below text. Sometimes it doesn't identify all of the ports on the card, but if you're looking for full acceleration for 1 monitor only, this could be the way to go. It's automatically enabled in the tonymacx86-snowleopard.zip and tonymacx86-P55BootCD.
