If you have a Mac 8800GT and a PC, and want to try (at your own risk!), here are the steps to obtain a ROM image:
1. Find a USB key that you don't mind formatting.
2. Download this program and install it:
http://i.thepcspy.com/USB_Boot.zip. It is a Hewlett Packard program that makes USB keys bootable, but doesn't only work on HP PCs. The archive password is pasta.
3. Use the program to format your USB key. Select the "Create a DOS Startup Disk" option and choose the folder "DOS System Files" from within the unzipped archive.
4. Once the disk has formatted, copy the rest of the files from "DOS System Files" to the root of the USB key. It may ask you whether to replace some files, say "no."
5. Download nvflash 5.57. Any earlier version will not work with the 8800GT.
http://www.techpowerup.com/downloads/819/NVFlash_5.57.html
6. Copy nvflash.exe and cwsdpmi.exe to the root of the flash drive.
7. Put the Mac 8800GT in the PC, be sure to connect the additional power.
8. Reboot your PC and boot from the flash drive. You may have to enter your BIOS settings and tell it to enable USB boot. On my Intel bios this involves pressing F2 at startup, and the option is in the Booting screen of the BIOS.
9. Once the flash drive boots up, type nvflash --save myrom.rom.
The file myrom.rom now contains a copy of the card's firmware.