|The led on the mboard is there to remind you to remove the AC power to the power supply when it's lit up whenever you fiddle with anything connected to the mboard or the power supply inside the case. ATX mboards are always being supplied with power in some places by their ATX power supplies even when the computer is not running, as long as the power supply is receiving live AC power. In most cases there is only one possible color. That led may light up even when the power supply is failing or something else is wrong.|
Failing power supplies are common and can cause your symptoms.
Check your PS.
See response 4 in this:
If you can borrow a power supply from another working computer, try connecting that.
One of the least likely possibilities is there is something wrong with the mboard, unless it has failing electrolytic capacitors.
Some mboards develop this problem - electrolytic capacitors were installed on them that were not properly made, and they fail eventually - the mboard manufacturer didn't know they were improperly made at the time the mboard was made.
Open up your case and examine the mboard to see if you have bad capacitors, and/or other findable signs of mboard damage .
This was the original bad capacitor problem - has some example pictures.
History of why the exploding capacitors and which mboard makers were affected:
What to look for, mboard symptoms, example pictures:
Home page that site
- what the problem is caused by
- he says there are STILL bad capacitors on more recent mboards.
Pictures of blown capacitors, other components, power supplies, fried Athlon cpus, etc.: