Funny, this is exactly the problem I'm having right now with my desktop, a gateway dx4200-09. (Swapped over to an Antec 500w PSU, 4 gigs of RAM rather than the default and an Nvidia 9600 GT) The computer was fine with this setup from this last january-february. Also, running windows vista home edition 64-bit.
So we turn on the computer, all the LEDs light up, fans turn on and it sounds like the normal second before you get that initial (I guess that's the post?) beep and the computer begins to boot up. But the beep and boot doesn't happen.
I've been poking and prodding at the computer with mixed results, but I've gotten confused at this point.
Before the persistant issues began, sometimes it seemed to have issues booting up. Chkdsks ran both before windows booted up and after revealed some bad sectors that were apparently not able to be fixed.
So just a week or two ago, someone else was using the computer (facebook) when it just turned off instantly, randomly.
The power-on-no-boot issue began.
Sometimes trying to power up the computer, it would begin the boot process but then stop at a black screen before the windows loading.
However, sometimes it would appear to be trying to boot via networking (would display network information, DHCP, try to find something though I've forgotten what now). When that wouldn't work, the boot process would not continue.
Sometimes managing to get into windows safe mode/recovery tools-only mode, was unable to restore windows due to bad sectors, and running the disk-recovery tool the first couple times resulted in the computer entering the power-on-no-monitor-signal state.
I did the reset/flush bios via the battery thing, powered the computer back on, ran the disk-recovery tool and met with apparent success this time.
The computer behaved for about two days, and it's back to this no-post-beep-power-on state once more. (I heard a message get recieved via xfire, and it blipped to its comatose state, heh)
The wife was just poking at the computer as well, and while setting up the date in the bios, it froze up, beeped and then re-entered that power-on-no-signal state.
Is it the HDD?
Thanks for any replies, as well. It's muchly appreciated.