Boosted the SB voltage in my BIOS (AI Tweak tab) from default 1.100 up to 1.150
The bios warned me if I tried to go higher by changing the font to yellow, then to purple if I went past 1.200. I could go much higher, so I´ll try some overclocks at this level. I polished the heatsink and applied Arctic Silver grease too.
Thanks for the advice locomoco321! This is the first time my systemś been stable in 4 months.
I spent 60 bucks on a new PSU and wasted way too much time on dead ends. Skyrim is waiting.