Peloche,
My bootcamp (v3.x) partition is on its own hard drive that is setup to dual boot XP MCE SP3 or Vista x64. I have had this setup and working for over a year with everything working fine with my 8800GT.
The problem though I believe has nothing to do with windows because the severe artifacting problem starts right away as soon as you choose to boot to "Windows" at the MacPro boot up section.
So here is what happens:
-Power on Mac Pro and hold "option" key.
-I am presented with 2 options: "OSX" or "Windows" and I select "Windows" and hit enter.
-The screen goes black for about 1-2 seconds and then comes up with severe artifacts all over the screen. This includes random ascii characters both in color and black and white.
-Now my RAID BIOS screen comes up and there are artifacts everywhere (I have a highpoint SATA RAID card that I only use in OSX to boot an external RAID 5 array). I have tried booting windows with and without this card installed but it doesn't change anything, there are still artifacts everywhere.
-Now my Windows dual boot OS selection screen comes up where I can choose XP Media Center Edition or Vista x64. (again random characters all over the screen but I can usually make out which option to choose and I have tried both Vista and XP. Both usually boot into windows and tell me I need to install the drivers for the new card but there are still artifacts everywere.
So because these artifacts are present during the RAID Bios screen and before windows even gets to a loading point, this indicates to me a problem with my card's ROM and the PC BIOS emulation of the EFI that the MacPro uses.
I do have a few Dell PCs that I think I will try the card in and see how that turns out but I need to reflash the card to the original PC ROM. I didn't make a backup of my ROM with the Hynix memory, but according to what you said to Astro768, the original ROMs have the same checksum correct?
The above pics are identical to my Sapphire Card with Hynix memory so I will search through the forums and try to find yours or astro768's original BIOS to flash my card with and then try it in the Dell and make sure it works correctly and go from there.
Let me know if you have any suggestions or if my thinking on the ROMs is incorrect.