hi Ulco
This is more or less guesswork but...
First advice would be to make a clone of your installation as soon as possible.
If something goes wrong (which is imminent with your problems I think) you`d only have to put in the cloned HDD and keep on working.
I get very nervous about those irregular hardware errors myself.
Then, most of what archonforest recommends.
1. Your Core-Temp is very old. Version 1.7x is it nowadays.
2. Your temperature is indeed very high overall for my taste.
3. Isn`t the Core i7-2600k rated with a burst speed of 3800 GHz max?
If so you are overclocking and should run it on normal speed for some time to see what happens.
4. You could take out the CPU and clean it and put new cooling paste on.
This stuff loses elasticity over time (especially when overclocking) and does not do its job as well as in the beginning anymore.
5. Let Core-Temp or any temp controller software run in the taskbar while working and watch the max temp the cores reach.
You could tell Core-Temp to warn you when the CPU reaches a certain temp close to tjmax.
6. Do yourself a favour and get a new Nvidia card. The error message you posted has Nvidia components mentioned (again).
You are wasting time clinging to this old model (budget is not a problem you told us b4). This should eliminate 1 possible malfunctioning device.
7. Is your HDD filled up to 97% (Space h:)? Or is that free space?
8. I forgot: what kind of PSU do you have? Even though the voltage ratings look normal (again comparable to my system)
perhaps there is not enough power overhead (anymore) for the strain you put on your machine these times?
If that was my one workstation for everything I`d start by changing the GPU, HDD and checking RAM (or even replacing).
Hope that helps a little. Good luck!
cheers, Klaus
ps: this tests your cpu. maybe it`s worth a try.
https://downloadcenter.intel.com/de/download/19792/Intel-Processor-Diagnostic-Tool