Crashed - Won't restart

I have an old Gateway GT 5012 computer I was updating for a grandkid. Pentium D 820 cpu. 4gb of RAM. 500 gb hard disc. Was working fine. Running Windows Vista and was updating a long series of updates when the computer just hung. After waiting for several hours, I finally pushed the start button and held it in for 10 seconds and did a hard shutdown. Waited and tried to restart it. Nothing. Will not go into POST. Nothing shows up on the screen. Was making the CD drive flash and acted like trying to read a CD but drive was empty. I finally disconnected both CD drives and tried to reboot. Nothing. Power light comes on, and light on the NIC comes on. Nothing else Any suggestions as to how to get it to at least go into POST? Using onboard video, LAN and everything else. Only one hard drive but was having no problems with it. Was going to swap hard drives, but not sure if that would affect it not going into POST. Tried to put Windows CD in and boot from it, but would never fire up the CD. No surprise. Figured it would not read the CD untill after it went into POST.
Thanks for any help you can give me.
David

 

Unplug the PC, remove the CR 2032 CMOS battery, and hold the power button for at least 30 seconds. Reinstall the CR2032 battery, and try to start the PC.

 

I will do that when I get back home tonight.

Thanks!

 

No luck. Unplugged machine. Removed CMOS battery, CR2032. Pushed and held power switch for 30 seconds (did this several times to be sure). Plugged it back in and it did the same thing as before, except now the case fan is running at full speed. The CD drive keeps flashing like it is trying to read the CD, but it won't even let me open the door. I have got it open, and there is nothing in it. I put in boot disc but it won't read CD.
Any other suggestions?
I don't have one of those little POST testers, but think I will order one.

 

I also tested the monitor on another computer and it is fine.
I then went and unplugged LAN, all USB's, CD's, HDD, mouse, keyboard. Still nothing. Nothing on the screen. I could pull the memory, but figured the POST would show on the screen before it checked memory. May try that anyway.

 

Did you check the voltage of the CR2032 battery? It must be 3.0V.
When starting the PC, it's normal for the CD Drive's LED to flash a few times.
POST is Power On Self Test. If it's not showing, there might be something wrong with the motherboard.