My family's main desktop computer died last week.  It had been flaky in
small ways for a while, like not always recognizing USB flash drives and
other small things.  One day on power up there was no video, no keyboard
response and a few blinks of the hard drive LED and nothing else.

Debugging by replacing major parts with known good components did not
solve the issue.  Power supply, memory, video adapter change outs one at
a time did not help.  So, I blamed the motherboard.

This evening I replaced the motherboard and CPU with a brand new set.  I
put these in the same case with the previous power supply, memory, etc.
 The new motherboard had built-in video so I did not install the
previous video card.

On power up, the new board displays the expected BIOS messages and boots
into GRUB.  However, during the boot the motherboard speaker makes a
clicky, screechy buzz on and off but mostly on.  Also the PS/2 keyboard
LEDs blink right after first power but keystrokes are completely
ignored.  I have not allowed it to completely boot yet, aborting at the
GRUB menu by either reset button or power button.

So, I am now worried that I have not solved the root cause, like maybe a
bad power supply.  Such a problem could have toasted the original
motherboard which masked the root cause when trying the known good one.
 Or, I could just have a peripheral connection screwy somewhere.

While I double check my connection work, I ask for any pointers.  Has
anyone on this list seen such symptoms before and found the problem?

Alan