Computer crashes on Idle state.

Hello,
first of all sorry if this article is in the wrong section i thought that i would get better support about my problem here. So let me begin, i just changed my graphics card from a problematic 6870 to a gtx 760. I love it so far, also i clean installed Windows 8.1 Pro instead of my old Win7 Ultimate. As for my problem, i was downloading something with uTorrent around 18gigs, i left the PC for about 2 hours or more and when i got back i had no signal and the PC was not responding to anything, it had crashed...i thought that this happened because of the (Disable monitor after some time setting in the power profile of Win8.1) so i changed it to no disabling at all. But today i left it again to download the rest of the gigs and when i got back it had crashed. I am really frustrated. (extra info: i recently changed my rams to slots 2-4 in order for my cooler to fit properly, i searched the web and i saw a recommendation about removing Asus Utilites i use Asus gpu tool do not know if i should remove it)
Thank you

There are no dump files in your logs. Please rerun the tool and upload the new logs.

Have you tried set to "Never" the computer in Sleep mode instead of disabling the monitor?

I found that when i'm set in High Performance Power Plan i can let my monitor sleep after sometimes but by not allowing the Computer to go in Sleep state, it works.