I restored system to an earlier state, then uninstalled RIVA, Afterburner, and everything related to graphic card. Then removed the video drivers from device manager and made it check for hardware updates to get the drivers again. Now it seems to work, I'll run some stress tests later (try to play games

)
Just a note, I have an SSD for system drive and it magically disappeared (there was no C: drive) in the middle of some install. I shut down the PC, took it apart to check connectors, then it was working again. Don't know if you experienced anything like this.
I'll post again later if anything happens.
Thanks!