HPS3120N, can sign in but after I do, the monitor goes to a diaganol checkerboard pattern and won't go any further. I have a new motherboard, now a friend is saying it's a processor. Help please.

It is probably not the processor. If the processor is bad, the machine will not boot and there will be no video at all. It could be the power supply, or video card, or memory, or that the processor heat sink and thermal interface material was not installed properly, or the monitor, or another device that is hanging the machine.

What happened that required a new motherboard and can you post a pic of "diagonal checkers"?

It is probably not the processor. If the processor is bad, the machine will not boot and there will be no video at all. It could be the power supply, or video card, or memory, or that the processor heat sink and thermal interface material was not installed properly, or the monitor, or another device that is hanging the machine.

What happened that required a new motherboard and can you post a pic of "diagonal checkers"?

That was what a friend recommended since the video was imbedded into the motherboard and the only way to change out the video card was to replace the motherboard.

Can you try the monitor on another machine?

Can you try the monitor on another machine?

We tried the monitor on another and it is OK. We also tried the desktop on other monitors on the same condition occurred. The same condition happened pre-new motherboard and after the new motherboard was installed. I agree I don't think it's the processor.

Try booting in safe mode. If you can boot and login in safe mode and everything looks good, aside from the low screen resolution you will need to replace the driver, you can download it from the computer or video card manufactures web site.