PC shuts down and will no longer power on unless the CMOS battery is re-seated.

Here's the specs of my PC.
casing: Dell Optiplex 790
CPU: i7 2600
GPU: Radeon HD 6700
Memory: 2x 4GB ddr3
Mobo: stock mobo for Dell Optiplex
HDD: 1 TB SATA(don't know the brand)
PSU: 700 watts generic
OS: Windows 7 Pro 64 bit
others are just the basic stock fans/heat sink from Dell Optiplex 790.

This PC is more like a hand me down from a friend.
I left the PC for about 4 months with no activity since my monitor died and I still don't have money to get one. I recently bought a 32' LED TV to use as the monitor(which i'm now regretting). When I powered it on, I was able to play for around 5 hours until I decided to stop since the TV is starting to hurt my eyes.. Later on when I turned back on the PC, it was still fine and after around 2 hours of playing, it suddenly powers off and I can't turn it back on. I thought maybe the PC is overheated since I haven't replaced the thermal paste for a long time. I bought a thermal paste and replaced it the next day and it still won't power on. Then I decided to replace the CMOS battery and now the PC is working again. I thought that was the end of it but after a few hours of gaming, the PC powers off again, The same thing happened, I can't turn the PC on. I decided to test the CMOS battery if it was discharged but when I test it, it still has some life in it. I placed the CMOS battery back and now the PC turns back on again. I had to change the date and time each time I re-seated the CMOS battery. Again, after playing around 2 hours, the PC turns off again. I re-seated the CMOS battery and it's now turning on again. I decided to shut it down and find out what's causing this issue.
now for the question:
1. Since I'm using a generic power supply, is it possible that the PSU damaged my mobo?
2. Is my mobo dying? (it's really hard to find a 1155 socket mobo replacement here at our country).
3. What other possible reason that can cause this issue?

Reply to legonaidas
No answers Last reply
More about shuts longer power cmos battery seated
Ask a new question Answer

Read More

Power Supplies Optiplex Dell Motherboards