PC shuts down at 3 am almost evey night

[arnnny]

Hi, I have this PC which had worked pretty well in the past 4 years. It's old I know. Before couple years I've upgraded it to support Core 2 Quad and installed Q8xxx series CPU. It has 8GB RAM DDR3, ATI Radeon HD 4600 series videocard with 1GB of RAM and Win 7 Pro 64-bit original. I never reinstalled it. It is used for video surveillance of only 6 cameras.

And in the past 2 years it has this strange problem - almost every night it shuts down between 3 and 3:30 am. Sometimes it lasts even for a week before starting again with these strange power off. I thought this is problem with power, but when I remove the feeding cable from the UPS, PC doesn't shut down.There are surge protectors there. If there some power surges, maybe UPS couldn't handle them. Recently it started to shut down very often and I saw a problem with video card cooler. I changed thermal paste on the CPU and video card and replaced video card fan only.   We've bought another 3120MT and moved HDD, CPU and video card to it from the old Pro 3120MT and the problems continue. Problem is that this computer is critical, because colleagues must go outside to watch what's happening. OK, old PC has one bad capacitor, I will change it. I've updated BIOS to 6.09, before replacing CPU.

[WAWood]

@arnnny 

Sorry, but I don't think we can really help you in this from here.

You've already isolated the problem -- the UPS.  When you disconnect the UPS, the problem goes away

I use UPSs as well, and they regularly update their monitoring software -- without telling me.  I have to manually go there and check for updates, which I do monthly.

Only thing I can suggest is that you check your UPS supplier to see if they have updated their monitoring software.