it seems to boot up again and the fans begin to run as before. I hear all the familiar sounds except for the computer itself posting. After about 30 seconds to 1 minute of uptime, the computer shuts down by itself.
sorry i had misread that to mean you had at least partially booted. Have you tried resetting the cmos ? Resetting the cmos basically involves crossing a couple of jumpers to remove all the old settings and restoring the bios to factory settings. Its done by moving a small block on the motherboard to cross a couple of connections, then moving it back. if you know how to reset the cmos, then please do so. If not, then please advise me of your exact model name and number of your computer and I will walk you through trying this.If your computer is custom built, then the model and number of the motherboard is what we need.We can try this and possibly a few more things, but I still believe its some kind of hardware issue. Perhaps one of your cables or connectors are faulty rather than badly fitted, this can happen.
Mitz from Tips4pc