I'm getting a problem which can occur between 5 minutes to 1 hour into playing a game. When playing a game, the graphics can freeze and the computer becomes unresponsive requiring a hard reset. Sound continues to play however. I've checked for the basic problems and ensured my drivers are up to date (updated to latest Nvidia drivers after the problems). I've also checked to make sure the GPU and CPU aren't overheating. Both are within safe bounds, with the GPU only reaching 69 degrees while playing Skyrim on High settings. Sometimes it can be a while before the glitch occurs, but makes games practically unplayable when it does happen.
So far I've only occurred the problem with Skyrim and World of Warcraft. I've tried disabling Nvidia graphics and using Intel HD for these games and it seems to fix the problem (as far as I can tell), so that's why I'm putting it down to my graphics card. Does this sound like a software or hardware fault?