If your PC shuts off without any message i.e monitor goes off instantly then it may be a faulty PSU try changing it. I had a similar issue recently changed the PSU and its working fine
Not only monitor, CPU also turns off
So are you sure I need to change my UPS?
I already had few problems with UPS before also so it will right to change it.
He's talking about PSU - Power Supply Unit - The SMPS of the computer.
UPS is something different. Yeah, if the UPS is not working properly, the computer may shutdown, but for minor voltage and load fluctuations, like addition of an external device via USB, the SMPS should ideally handle the situation.
Do as he said, connect your computer to the mains, without the UPS, and see if it shuts down abruptly. If it still shuts down, then the UPS is alright.
Regarding the malware scan,
PLEASE do a full system scan using spybot search and destroy, AND some good antivirus program.
I am starting to get irritated now that you're not wanting to follow simple instructions. If you want help from someone sitting 10000 km away from your computer, without him having any sort of access to it, you might have to do certain things which he tells you to.
You still havn't answered a simple question, which windows are you using?
And, if you still don't wanna do it, Post a HijackThis log, and I'll have a look at what may be wrong.
Get it from here:
HijackThis - Trend Micro USA
If you need help, you should be willing to cooperate. Else, this is my last post on this issue.