I was just having a similar issue with the 660m in my laptop.
turns out there was a setting in the nVidia control panel that set the preferred processor, which was set to auto select. i set it to prefer the gpu and it started running fine.
Don't know if its related but it might help.
thank u for trying to help but that has nothing to do with the desktop (thats cause you have 2 gpus the built in one [INTEl HD] and the nvidia one)