Flickering screen caused by damanged motherboard?

Hi,

I ran an ATI Radeon HD4870 on a COoler MAster 500W PSU in my computer and it worked fine for a few months, then I started getting blue screens and also flickering screens. I realised that the power supply may not have been sufficient? I've replaced the PSU and the blue screens have stopped, but I still get an almost constat flickering screen. Things I've done so far are:

- replaced the PSU with Corsair CX600
- replaced the ATI with Nvidia Geforce 9500GT to test
- replaced the monitor to test

After all this I still get a flickering screen. Does this mean that there may be damage to my motherboard or CPU? Is such damage possible given the situation? And what should I do...?

Any help would be much appreciated, thanks!

Specs:
CPU: Intel Quad Core 2 Q9400 2.66Ghz
Mother board: ASUS P5Q PRO (EPU) P45
Graphics Card: ATI Radeon HD 4870; then tested with Nvidia Geforce 9500 GT
RAM: Kingston 2x2GB DDR2 800
PSU: Coolermaster 500; then upgraded to Corsair CX600
HDD: WD SATA 750GB
Monitor: Dell 2209WA; then tested with a BenQ monitor

There can be number of reasons behind issue you are facing. I am listing them one by one so that you can perform some more test. This board does not has a onboard video connector. So here it is not possible to check directly by connecting the monitor to motherboard.

Flickering screen is caused by :

• Outdated GPU Drivers.
• Incompatible GPU
• Multiple GPU Drivers causes graphic failure
• Damaged or improper PCIe slot on which GPU is attached
• Damaged or improper monitor cable connected to GPU
• Damaged or improper Graphic card

The thing which you can do, is first check the monitor cable. Second when you had attached ATI GPU, did you removed the old Nvidia drivers from your system. If not then go in Control Panel and remove any of present drivers. Re-install ATI's all latest drivers and updates in your system. There should not be multiple drivers installed at single time in your system.