Recently I purchased Radeon HD 5770 made by sapphire, because BFG 8800GT OC I used to have failed miserably. This is what I did after plugging the new card in.
1. Remove old drivers for nVidia.
2. Download and install Cataclyst Control Center from ATI website for HD 5770.
3. Update BIOS.
The problem is, the computer crashes. Not often, but this happened only when WoW was playing. The screen goes dark and with stripes, everthing becomes non-responsive, whatever sound was coming from speaker starts to loop.
I cleaned dust thoroughly before installing the new card. I consistently checked temperature of new card but it was never higher than 60 C. I am quite at a loss. Any ideas on what the problem may be? (I might be wrong, but this seems to occur more if the PC was turned on a few minutes before)
For your info, I add my computer spec:
(CPU) Intel Core 2 Duo E8400 3.00GHz
(Motherboard) ASUS P5QL PRO Core 2 Duo P43 Intel with PCI-Express
(Memory) I believe it has three 1GB sticks from Kingston. (DDR2-667)
(Power supply) Antec 500-watt max EA-500D --- plugged to HD 5770 with a 6-pin.
I am told that HD 5770 is more power efficient than 8800GT. So I am convinced my power supply is sufficient.
You got it a bit wrong.
You should have uninstalled the old drivers with the old card still in the PC. All is not lost though you can run Driver sweeper (free download) to check for any left over bits that may have been left behind. Some people say its good practice to use it when switching from Nvidia to ATI anyway.
Also some people are having issues with the new 10.6 drivers so if you are using those try some slightly older ones. Im using 10.3 at the moment.
Why did you update the Bios ?
I updated the Bios (actually, my computer was already up to date I believe) because my old graphic card 8800GT had issues and I was told Bios update is important for it to work properly.
Here is my suspicion. Realtek HD Audio may be conflicting with whatever HD sound support that comes with HD 5770. Once or twice, I was able to recreate the computer crash:
I have a speaker as well as a headset. To use headset, I plug in the headset to front panel, which opens up Realtek HD Audio manager(I believe a part of ASUS motherboard), showing that I plugged in headset. When I plugged it out, it failed to go back to the original speaker for sound output and crashed. This happened while running the game.