Well I flashed my Card in Tiger safe booted (I hear thats the best way to do it) now i don't know if u have tiger But I know harrymatic Has some sort of guide some where and i believe he flashed his card in Leopard. to flash the Graphics card U tape Pins 3 and 11 on the card insert it into ur G4 then you download this http://thomas.perrier.name/graphiccelerator.html and you find the FireGL X3 ROM here http://themacelite.wikidot.com/wikidownloads2 then you copy the contence of Graphicscelrators DMG onto ur desktop along with ur ROM then you open the graphiccelrator app then go to the ATI tools folder and Run me first then run ATI multi duper to back up ur PC card ROM (and any other ATI cards installed at the time) then once u have ur backup you go back to the graphicelrator app and in one of the menus in the menu bar there will be Install mac ROM into ATI multi flasher click on that it will ask you for ur Mac rom select the one you downloaded from the web then it will ask for a ATI Multiflasher and u go to the ATI tools folder and select the one there then click ok or so and it will install the ROM into the ATI Multi flasher then once thats done You open the ATI multiflasher and it should say do you want to flash something like R420 in slot 1 and you click on YES then it will proceed to flash it If it asks to flash any thing els like ur PCI GPU say No then it will close and u can close every thing shut down ur mac attach a display to the FireGL X3 and turn the mac on if every thing went well u will get a display
I hope this all makes sence and I belive u should install the ATI 4.5.7 Display update... oh and i see harymatic beat me to it LOL well Ill still post this it took way to long to write up just to throw away LOL