mb does not BOOT, although power is on

I have two accounts with the same experience:
1. A LX mb
2. A B2F BX mb

over 9 out of 10 times, I plug in the power socket to the
motherboard, the mb starts the fans automatically.
But, there is no beep, nor boot process.
But, at a race chance (~5%) the 2 mb boots without
any problem.

both mb are about 3 years old, and the power
supply would power other new mb without
any problem (everytime, it boots).

Any suggestions?

Check your connections on the board from the power supply. I had that scare too recently. I was upgrading my computer but something didn't fit right so I reinstalled everything back. But when I turn on my computer nothing came on the screen and no beep. I was very ****ed that I burned my MB, but luckily the next day I was so bored that I cleaned my power supply *don't ask* and I plugged in everything. And for some reason I plugged in the power supply to the MB tighter and it worked. Probably it was only a little bit in and not all the way. so check your connections.

thank you, but I did try it very carefully

I did try the PS with Mbs very carefully.

Also, when I use the PS with new mbs (2 new mbs).
They work perfect, a snap!

Then it could be a capacitor on the MB thats busted.

which one?

Since 2 mb had such problem and actually one
computer in our office also starts to have boot
problem similar to these --- i.e. the fans are
running but no beep nor boot process.

Sheng

try clearing your CMOS. Try pulling out all your cards except video, and try booting. Might be one of the cards causing it to not boot. Try some different memory, if you have any extra lying around. You pretty much want to start by trying to boot a bare bones system to rule out various things, and go from there.

With the age you indicate you may have cmos battery probs. Radio Shack will have your bat change um and see what happens.

Get a 1 known working PCI video card from a working computer
(AGP if you must)
Then get 1 Stick of Know Good RAM from a Working computer.
Then Get 1 KNOW good PSU from a working computer

Place the video card in... 1 stick of ram, and the PSU.
Nothing else should be pluged into this motherboard.

Try to power it on. The PSU fan should be spinning correct?
If you dont post... Remove the battery, clear the CMOS.
Then try again.
Still no good? then you may have a dead Motherboard.
I have delt with ones having the same problems you have been discribing.. boots every 15th try or so.

Thank you very much!

Thank you all vrey much for all the suggestions.
I will give that a shot.