Random rebooting-VERY annoying

For no apparent reason (known to me) this thing just won't stop the random rebooting, which some times is hourly or sooner. Tested memory with both memtest86 adn the windows diagnostics thing, both came back flawless so it's not the ram (#132 error in WOW had me wondering), I haven't installed anything for months either. Ran multiple virus scans, not even a harmless adware found, probably thanks to this barely ever being connected to the internet. Now on to the actual errors. 95% of the time I will be in the middle of something, important of course, and it just reboots as if I hit the button. But since it has a plastic cover over it that needs to be lifted up and then the button pressed, it's not an accidental push of the button. Other times it "tries" to help by showing me a BSOD but with no writing on it, oh how helpful that is. Every once in a while it will pop up with that "Severe Error"/"Error Report" thing and sends like 5 of them the most recent time they were "Corrupted","Memory Error"x2, and a "Video Driver"x2. Since the corrupted one talks about recently installed software or hardware, I don't know what to do about that one, nothing new for almost 3 months now. As I said before I tried the memtests and they came back with nothing, and I just reinstalled my video drivers, but it still happens. Any ideas?

Specs of computer?

Age and rating of PSU?

PSU. PSU PSU PSU.

What you've described is the symptoms I had when the first ANTEC Psu died. Then the 2nd one died. I'm on the 3rd and an ULTRA PSU as well.

If you've got a cheap one, put a fork in it because it's dead.

Not getting into the debate about MBM and the accuracy of the rails, why not check the voltages and see if your 5V is under 4.85 Vs....

yeah it definetely sounds like the PSU.. check your voltages with a Multimeter.

My gigabyte had me worried, said I had 3v on the 5v rail till I noticed no drives, were dropping out and no reboots were happening. Tested it and the PSU is rocksolid, just it doesnt like MBM5

I had spontaneous rebooting problem and I finally narrowed it down to a bad PSU. If you have a DMM, try checking your 12v reading on one of the molexes - if the number is low or is jumping like mine was, then it's time for a new PSU.

this is also a telltale symptom of an overheating CPU- reseat you CPU and use a good thermal compound.

Ok got MBM5 up and running. CPU is 55-60C (That seems hot?) Rails are:
+5: 4.87
-5: -5.04
+12: 11.67
-12: -11.86
There all dead steady too, haven't noticed a flux in the 5 min I watched it

The only thing I know about it is that it says Premier 300W on the side, along with both a Pentium 4 sticker and an AMD Reccomended sticker, which I find weird. As for specs: XP pro, Athlon 2000+, FIC AU13, DVD burner, CD burner, 80 gig Maxtor, 9800pro. That's about it. If it is the PSU looks like I'll be buying that case I want sooner so I can put the PSU it comes with in this case, because 450W won't run the X2 4200+, 7800GTX x2 SLI'ed and the beast of a wc system UI want to run in the case.

It's good that it's steady, but 11.67 is pretty low. Leave your DMM on and run some programs such Prime95, SuperPi, or even a graphically intense game to see if the voltage fluxuates under load. Also try rebooting and watch the voltage. If you see lots of changes in voltage, chances are you system is drawing more power (amps) than your supply is putting out. If you're planning on upgrading your system, a good quality PSU is a great place to start.

You can get 10 dollar PSU's that are "able" to run a Intel/AMD top of the line chip(for a week if you are lucky), a sticker to me tells me nothing until I have heard from a few different places and a lot of different people that X Co. makes good parts.

Then again, I have issues with Antec/Tt and a few others that make compnents. I have yet to have a Antec PSU that lives for more then a year stable. Tt makes some good parts and I like their Case/HS but their PSU and fans are something that leave alot to be desired. I have a few no name fans that put more CFM out then then stock fans that came with my Xaser case.

YMMV though.

Use a multimeter to get a better version of your voltages. MBM5 says my 5 volt is dangerously low(+/- 3v on average) and that my 12v is running under 11.2 usually. I ordered a new Fortron PSU to replace it but after having to RMA the Fortron I got a replacement multimeter and tested the rails. To my suprise the Aspire Chameleon that I bought awhile ago, is actually rock solid stable with voltages at Idle of 12.5, 5.5 and 3.7. I leave MBM up to get a heads up if there is possible problems, but I dont trust it solo. My MB is just reporting incorrectly. I havent had any problems that I should have with a low/flucuating PSU.