Hello.  I'm having a serious problem with my computer.  I just built it yesterday.  Specs are here.  Anyway, I start it up, and it runs fine for a few seconds, even enough to where it gets all the way to the BIOS main screen, and then just shuts off.  I was told it might bee an underpowered power supply (it's the stock from the case, and is 500W).  If you guys have any ideas, I'd greatly appreciate them.Same thing happens for my home built computer. Except mine will turn on then isntantly back off, so i dont know what is wrong.Not sure about the first query, but I had the same experiences with my new build and you need to be careful that your motherboards power connections are correct, the 4point SPECIFICALLY with mine, I had used the breakaway part of the main power lead instead of a completely seperate 4 pin lead...Recheck bios setting......to defaults.....check that there is notting lose like video card....etc.....check the ide cable on the hard drive is tight.......  Is fan spinning on the cpu?All the fans run fine.  I just went and we installed the cables to both the cd drive and the hd.  The vid card is secure.  I can't CHANGE any BIOS settings, because it won't run long enough to get to the BIOS menu.reload the msi floppy disk that came with the mobo....did you put artic silver paste under the heatsink......any beeping on boot up???Huzzah!!! I fixed the problem.  What happened was I improperly installed my heatsink/fan.  I didn't get the pins in all the way, so they were a little loose, thus making the cpu connection loose, and thus triggering the power down.  I't running fine now, and I'm roughly half way through formatting my 160Gb HD.  Thanks for the help, everyone.It always something silly now load an anti-virus program......and a firewall on it.......before connected it to the net.........dont undo the work you have DONE I did have a SIMILAR problem but it the time between shutdown was varied.  I could never seem to get windows installed befor it shutoff.  Turns out when my cousin mounted the mobo he didn't use risers and it shorted out through the case right under the processor socket.  Rather large crater left in the metal on case .  It worked after using riser but it was slow and didn't like a heavy load or it locked up  .  Stuck that stuff on my "tech trash" shelf .