I recently built a machine with a Gigabyte GA-p55-UD2 motherboard, a Gigabyte 9600GT video card and a core i7-860 processor. When I tired to install Windows 7, the machine froze after the reboot where the video driver is installed. I could not install windows 7 at all. I tried Vista and that went well since Vista does not install a video driver during the installation. But after I installed the driver, the system froze. So I assumed the video card was bad and sent it to Gigabyte for repair. Meanwhile, I installed Windows 7 using an old video card.
Gigabyte said the card was fine and sent it back. I tied it again in the already installed OS and it failed. I then tried a Radeon card and it would work for a while and then blue screen. So I assumed now that it was a MB problem. (The memory checked out with Memtest.)
On a whim, I put the 9600GT card in the PCIe-X4 slot and lo and behold, the system ran fine and has been stable for two weeks running two 24" monitors. My question is, what am I losing by using the X4 slot instead of the X16 slot. I am not a gamer but got the card to support two monitors. If I replace the MB with one with a working X16 slot would I notice any difference? I just hate to send the board back and be without a computer for two weeks. Are there likely to be any other problems in the future with this board?
Firstly, try update your motherboard BIOS.
Second, the PCI-E x16 slot was provided by the CPU due to 1156 architecture, so there's quite nothing to do with the board. Maybe you could try to borrow another CPU from your friend to test it out. Running on PCI-E x4 will have a certain data transfer bottleneck compares to running it on PCI-E x16. Of coz it does not make any trouble to run in dual monitor. PCI-E x4 slot came from the P55 PCH.