Screen turns off after installing dri...

Hello. I have a really annoying prolem on my GF 6800GT. Firstly, I have formatted my whole computer and re-installed XP, drivers and so on. When I install Nvidia drivers, at 50% it tries to apply the driver, and my CRT monitor turns off (The screen goes black, even it is on; so it doesn't have a signal). I've tried 5 different nvidia drivers for my videocard, and some of them get installed, but after reboot CRT turns off again.

I think it has something to do with the DVI to VGA adapter. Even though I've tried 3 different adapters, I think the problem is somehow with them. And I also tried to use the adapter on my dad's LCD-screen, it didn't work either. I suspect that DVI to VGA adapter doesn't support either my card/any of these two screens (CRT and LCD).

Would buying a DVI cable to the LCD-screen help ? Would it work then ? I'm really annoyed by this problem because I got this video card 3 days ago. :/ I wanna play on it because my old Radeon 9600 Pro sucks...

So:

1. The problem can't be drivers, because I've tried 5 different drivers, and all of them should be compatible with XP and 6800GT. And I formatted PC and re-installed Windows XP Professional so ATI drivers can't be haunting anymore.

2. I don't have an onboard graphics, so they're not conflicting either.

3. My motherboard DOES have Nvidia Ethernet and IDE, so I first thought that they conflict, but it didn't work on an different motherboard either. So motherboard is fine then.

4. My PC identifies my 6800GT in VGA-mode (The mode where you have to press 'F8' to go there) so the videocard is working.

5. Power supply is strong enough, 350Watt and for 12Volt 20Amps.

My conclusion is that DVI cable for LCD-screen would solve the problem, but I'm not sure so I'm asking from you, experts. ;) I don't wanna lose my money for such cable if it doesn't work on it either.

However, I wonder why Windows installed some drivers automatically when I used my dad's motherboard, and on my own I had to install them myself. I thought that the videocard works on that motherboard, but it wasn't the problem because when I rebooted it, the same problem occured.

My specs:

ASrock K8Upgrade-NF3
AMD Sempron 2600+
1,5GB DDR400
Nvidia GeForce 6800GT 256MB

My dad's specs:

Motherboard I can't remember, but I think it's some ASrock too...
AMD Athlon 2600+
1GB DDR333
ATI Radeon 7200 (or sth like that)