Hey all.   I appolgize for the novalistic post but details are everything.  I finally built my new PC and it is great.  

However, I was trying to fix my old one but am having troubles.  It won't boot up.  I have been troubleshooting it for a while and was pretty sure it was the MB.  I bought a new MB, installed hooked everything up and still no joy.  

A strange problem I discoved that I thought was the result of a bad MB is that as soon as I turn on the P/S on the back of the Case the PC powers on and I can't turn it off unless I flip the P/S swith back off.  Once it does power on the HDD activity light comes on but never goes off and I never here the internal speaker beep.   ???

I disconnected every component except 1 stick of RAM and still same problem.   I swtich the sticks and same result.   The only thing I did remove is the CPU which I don't even know if i could boot w/out a CPU.  The whole system is only two years old.   AMD XP 2200 with Shuttle MB.  Would a bad CPU Cause nothing to happen?  

I even went as far as to check all of the voltages coming from the P/S and they all checked out with what the MB said they should be.  I really don't get why as soon as i flip the swith on the P/S the system powers up and can't  be shut off.  

I am at a loss.  The only thing I haven't tried is swapping the CPU out.  

Something i just thought of is if the CPU fan is spinning too slow it would allow a boot up to protect the CPU.  I had that happen to my old AMD 400.  I replaced the fan and it worked.  

Still I think I should be able to get into the BIOS.  

Any thoughts would be great.  

Thanks Congo, but what about it not booting up?  It started doing that on its own before I even switched MB.  It doesn't even initialize the HDD, Flopyy OR CD.  I will,however, check the wireing and make sure its it correct.

Actually, yes there was, quite a bit, but I can't see it here...... maybe it got pulled for political reasons?  

It's very late here so I'll just give you a brief and you'll have to figure the rest out logically.

Forget about what the PC used to do, clear your head and start basic system diagnosis.

There is no doubt that the case wiring was in error. Every symptom you describe supports that.

There is some possibly relevant info in this thread:

http://www.simviation.com/cgi-bin/yabb/YaBB.cgi?board=hardw;action=display;num=1...
However, there is a very complex array of possibilities, so you need to be particularly careful and use near scientific methodology and a process of elimination.

2 things to try first in no particular order,

Reset CMOS defaults by mainboard jumper. Try to get a post. You need to know the correct procedure for this.
-unplug PC
-place reset jumper in reset position for at least 30 seconds
-replace jumper to "run" position

Strip ALL drives and peripherals (disconnect the wiring, no need to physically remove them.) Try to get a post.

I cannot emphasize how important it is to remove all drives etc. This establishes whether or not you have core component problems, ....... until you get the core running, there is no use of having other complications thrown into the mix.

You need, CPU,RAM,Video (with monitor plugged into the active video card outlet, if you have onboard video plus an addon video card, check to make sure the correct one is plugged into the monitor or you may see nothing until you do. Usually, resetting CMOS defaults video to onboard if fitted.

Make sure the new mainboard's jumpers are set correctly, if the Reset CMOS jumper cap is in the wrong position, you won't get a boot.

If there is a manual overide jumper that takes control away from CMOS for basic system boot settings, that needs to be set to auto....... or you need to correctly configure the other jumpers so the FSB /CPU/RAM speeds are correct for your hardware.

Does your RAM support the mainboards default bus speed and ram timings?

Check All wiring and connections again, try a known working PSU of higher wattage.

Panic er, I mean, it will work out I'm sure!