again this is fresh install
disk with trojan has been replaced so this make no sense
i dont install anything at all
just only the videodriver and seems its all been related too that!
Let me see if I understand things right now:
You did a fresh install of the OS and the computer ran fine.
You installed the video driver and things went to running bad/slow.
I had something very similar happen to me before. I tried multiple OS re-installs, many different video drivers and 3 different video cards....and I always got the same results:
1) The system would just lock up
2) The system would BSOD (usually it would lock up)
3) The system would run very slow if it didn't lock up or BSOD
I knew that the RAM was good, I tested it in another computer - no issues.
I knew that the GPUs were good, I've used them in previous builds.
I knew the PSU was good, it powered a more power hungry build without problems.
I knew the HDD was good - chkdsk showed no errors and the HDD was just taken from a previous build and it had no issues. The HDD was formated and had fresh OS installed (Vista and XP were tried - this was just before Win 7 released)
My steps taken:
Format HDD and installed OS (Vista) - everything runs fine
Installed motherboard drivers - everything runs fine
Installed Windows updates - everything runs fine
Installed GPU driver - fails, causing BSOD or lock ups
Uninstalled GPU driver - fail, unable to uninstall in Safe Mode
So I started over. I formated the HDD, re-installed everything and tried a different (known working) GPU driver and the system locks up. I went through this process nearly 2 dozen times. I used different GPUs, I used different GPU drivers and I even tried another OS (Windows XP). The same issue happened over and over again.
I replaced the motherboard and not a single issue since.
I'm not saying you're having the same issue I had, but if everything runs fine after the OS is installed and once you install the video driver and things run like crap it sounds similar to my experience.
Have you tried another video driver?
Have you verifed the GPU works in another computer?