Hi everyone, I'm new at these forums (by posting) and I just wanna add I apreciate everyone trying to help. I also have bought two of these HD4870 cards (Powercolor brand) and after editing one of the BIOSes with Radeon BIOS Editor and flashing both cards... cards just don't boot any more at all. They were working fine about 1-2h after the BIOS flash and just as I wanted to close the case and wanted to boot again there was just no boot... PC just dead. Fans are working but I get no screen at all.

I have an HD3870X2 running now and 1 of the HD4870 connected, trying to get these cards working again. I don't know where some of you are sugesting to check voltage on the card, all I can say right now is I used the voltmeter and it's showing around 11.99V on the pins on the card where the 6-pin PCI-E power connection is. I don't think it's the PSU, I think it's bad BIOS in the card itself... maybe the flash went corrupted (although unlikely to be the same on both cards the same way) and now it just won't get back to original... I don't know really... I feel regret to doing this right now... but what's done is done...