I'm using XP pro SP2, 762 DDR, Asus P4B533M Mboard with socket 478 Pentium 4 133mhz,

It all started with my computer prematurely shutting down while playing games or using media player,

instant messaging or working with office programs.

I have done the following:

1. I installed Asus probe to monitor the voltage, fan speed and temperature of my CPU & my board

showing no alarms at the moment

1. Clean and dusted out the the motherboard it's slots and the casing using an air compressor.
2. I have changed the power supply to a new one.
3. I have removed and reset the CPU fan along with the heat sink and applied new thermal comppund.
4. I performed a virus scan of my whole computer.

After the cleaning and changing to a new power supply secondary problems such as:
Floppy disk(s)fail(40) msg has occured.
Shutdowns are more frequent now (7x just yesterday).
My primary slave HD is detected but is now unknown in Disk management console. Consequently, a disk

wizard is now showing and giving me an option to initialize that disk. Who kwows what may have happened

to its data?

Do you think my Mboard has gone haywire?

You have done good so far in what you have tried.
So far it appears somthing is damaged.

I suspect either your old power supply malfunctioned at some point, or you had a power spike or surge and you weren't protected from that, or weren't adequately protected from that. Any power outages or nearby lightning lately?

"Floppy disk(s)fail(40) msg has occured."

I have seen 4 or 5 computers with bad power supplies where the first thing they killed was the floppy drive. In one case the current voltages in the bios looked fine, but booting from cold - the computer cooled to room temperature - and using a Windows monitoring utility - showed the voltages were way too high for a few minutes, then they would fall to normal and stay there. The damage overvoltage can do is hard to predict, but the higher it gets, the faster it will damage anything connected to the power supply. Somtimes the power supply doesn't exhibit that there is anything wrong until an extra load is put on it - such as when you are playing a game, or burning a CD or DVD.

I have seen where a bad power supply has damaged the board on two cd drives - they could no longer recognize a CD. A malfunctioning CD drive can sometimes cause strange symptoms. Make sure your CD drive(s) work(s) properly - if one doesn't, disconnect it's data cable.

"Shutdowns are more frequent now (7x just yesterday)."

Are these black screen, or blue screen, or the computer just dies?

A failing hard drive can also cause strange symptoms. Get a diagnostic utility from the maker of your hard drive's web site(s) and test your hard drives.

Yes we have outages but my UPS is as good as none since I'm away from my desktop during most of these occurances

My floppy drive must have toasted during that shutdown before I dusted out my machine. I just disabled it in the bios to rid the hold up at startup.

Since window no longer detects it, I also tossed my primary slave hdd by disconneting it. Eversince I've had less shutdowns, only once or twice yesterday.

But since once is too many in these instance, I changed a supposedly new power supply and so far so good today. I hope the elimination process stops here.

By the way, should I trust my Asus probe software or any at all? After a good run this am (the PSU). It went haywire just this afternoon for a good 15 minutes showing voltage spikes of 13.28v and to as low as 2.58v. on the +12V guage, MB temp escalated to consequently and my CPU fan when to a ballistic 6000.

Interstingly, my CD-R drive has been malfuntioning long before the shutdowns.

Thank you tubesandwires for a very precise, informative suggestion.

"By the way, should I trust my Asus probe software or any at all? After a good run this am (the PSU). It went haywire just this afternoon for a good 15 minutes showing voltage spikes of 13.28v and to as low as 2.58v. on the +12V guage, MB temp escalated to consequently and my CPU fan when to a ballistic 6000."

Asus Probe is as good as any - it is merely interpreting the outputs of the hardware monitoring chip(s), just like the bios does.
You could also try a freeware motherboard monitoring utility, with Asus Probe turned off. These Windows utilities are the only way you find out about transient problems like that. Often by the time you look in the bios, the problem has gone away by then.

In this case the old PS could have damaged the mboard, so when you get transient problems like that it would be best to try the PS on another computer that you know works fine, with some kind of Windows hardware monitoring utility running - if the problem appears again, you can be pretty sure the PS is no good. If it doesn't there's a good chance your mboard is damaged.

Try the slave drive you took out on another computer - if the mboard is damaged, there may be nothing wrong with it, or it may be fried too.

You could also get a diagnostic utility from the maker of your hard drive's web site(s) and test it.