4870 black screen after windows green loading bar

When I turn my pc on, everything goes fine. but after the windows vista green loading bar, the monitor (HP W22) goes black screens and "no display, monitor going to sleep". I then figured out it is the display problem. I had tried sweeping and reinstalling the driver, but still doesnt work. Im getting really tired at this. I have to boot windows in low resolution mode everytime (sometimes wont work!). I googled for every solutions but wont work. Is ATI ever gonna come up something to fix this? I was a nvidia fan but I decided to give 4870 a shot. So far, Im VERY disappointed.

Help me!

AMD Phenom II x4 940
Gigabyte GA-MA790X-UD4P
8 GB G.Skill PK DDR2-1066
Corsair 650W
Sapphire 4870 1gb
Windows Vista 64-bit
HP W22 monitor

I would guarantee that Zip is correct. Op try using Driver Cleaner, it's a free app that you will use in safe mode. Select to remove all nvidia files while using the app. Then install the new driver.

Yeah, go to nvidia's forums and see how many morons post on there about how they cant get their cards to work, doesnt mean theres not a million other people out there with the same card and same drivers and it DOES work.

Go to ATI's forum and type in atikmdag error, people been trying to figure it out for a couple years now, lol. Took me about half a day to figure it out. Classic case of nvidia/ntune/rivatuner drivers conflicting with CCC, but yet for years theres ongoing forums about the problem.

Theres no issues with 4850/70 and Vista64 with 9.3 or 9.4 drivers because I've installed several of them including my own and they all work flawless.

Are you sure you loaded the 4800 series drivers for VISTA64? Are you sure you got the latest motherboard chipset drivers? Latest DirectX drivers?
Are you sure you have all the proper power cables to the video card?