When i shut down my computer and try to restart the computer will not boot .  power to PC comes on and the HD, CDR and DVD lights are on however the computer just appears to be in a locked configuration.  no images on monitor no keyboard  capability.  reboot or power buttons on computer do not work.   the only thing that stops the system is to pull the power plug on the computer, wait 10 seconds attach power cord and then start computer.  everthing will then work correctly.  system will rebbot from the start directory without any problems.  the above procedure is constant. shutdown always requires a power disconect   before the system starts.  tried a hundred different things no solutions,  runing windows 2000 with all the updates, mcafee virus software  What are the specifics on the machine? Do you have a known good power supply to test with?amd motherboard , ram 512.  ATX 400 watt power supply (new)  160Gig HD , aopen dvd, mitsmi CDR. replaced  the battery , upgraded the BIOS, using 56k modem.What brand power supply and why was it changed? I TAKE it the other components are used? What has happened from the time it worked right until now? What AMD motherboard?mother board made by hsing tech,  now owned by ecs. model m830LR.  

nott sure when i noticd the problem or when it started, upgraded powersupply the old one burned/(overheated)

somehere between adding a  new DVD burner and installing the drivers , reinstalling windows 2000, (operating system had bad virus) the system just stopped working correctly.    i also purchased one of those PC analyzer board.  that didn't help it just gives me a code but no resolutions.  I also swaped out the VIDEO card,  no change changed the inside cables, no resolutions,   reset all values in the boot sequence , no help.  swapped out the key board and mouseCould have ruined the motherboard during the PSU baking. Has it ever run right after that?yes system came right up after installation of PS,   sytstem worked fine for ?  not sure when the problem started , turned it on one day and nothing happened, thought I had a hard drive failure , shut system down and rebooted with a  boot disk.   only after a lot of  no starts did i reconginze the pattern, shut it down pull the power cord plug it back in and the system works fine always same sequence . no varience all the reakl iat people come up with a different solution.  it's  kind of i am going to fix this thing maybe???  Hmmm...

without any other info, I sense another extreme overclocked system going belly up.

The original PS dying is a hint.

Display freeze when graphics and memory are overtaxed/overheated.

Numerous restarts before it will boot also hints at overheating until it has a chance to cool off.

Cooling system is probably insufficient.  Graphics card is probably red hot and the PS is trying its best to keep up.

But, these are just a guess until we find out how it's being used and what you've got running in it.

If you had a nasty virus buried in your root directory and didn't fully reformat before reloading the OS, then he could still have that problem too.

As a starting POINT, I'd recommend you remove all peripherals/hardware not required to boot your system (modem, DVD, etc.).  If your problem goes away, you can assume you're overtaxing your system.  If your problem persists, tell us how you checked for virus/malware, how you reloaded your OS, how you checked to make sure your graphics card was good (under the same stress as your PC), how you decided that your new PS was sufficient for your system, and anything else you might think is related.

Dell

DellI disconnected all of the perphials one at a time untill all were disconnected , no change,  I updated the power supply from a 350W to 400W no fomulas used. the computer came with a 350W. I let my virus software get out of date and had house guests using the computer for two days. the results were system crashes, lost files software wouldn't boot and all the other things that happen when your system gets corrupted.   I had to Reformat the HD(s), which I replaced with one new drive.  I reloaded the OS from a CD. up-dated the Mcafee software and up-date it everytime I  go online.  also run Spybot .  I replaced the computer clock, and swapped out all the internal cables.  I replaced the video card with another card from a different computer no changes in performance.  I tried  booting from a CD or disk instead of the HD same problem.  How much was that 400W PSU ? ? Anything under 75 bucks and you are back to square one i'm afraid.I think it's time to pull the  plug  and update the computer??? might be expensive , but less agravationDon't give up.  I think you need a Mother board,  New one or Ebay one,  Heck, you sound like you have spent 400 bucks trying to fix this one, Retreat is not an option  

I did not see if you tested running with one stick of ram.  

Or take out all the the cards ,  and blow out all the sockets and things,  wipe the connects and re-insert

I also grab the case with one hand and run the back of my finger over the chips to see if any are red hot.

Bios also has some real low safe settings

I once have had the MB sound on and a sound card and that made fruity things occur

SC