About 4 days ago I turned on my PC and booted far cry 3 (ultra) to play and it was running at 5-20 Fps, a huge change from the 50 Fps I was getting the previous day, I exited everything and checked my cpu consumption at the desktop which was very high so I assumed it was a virus, I have since been in touch with an expert at malwarebytes forums and after testing everything I haven't got a virus, we are sure of it. My pc is still running much slower. Here are my specs:
I'm sure someone will take issue with this, but I'm just going to relay my personal experience.
Around Christmas, there was a big Amazon sale on Darksiders, so I picked it up. I don't have the world's greatest gaming system, it's a first gen Core i7 860, 8GB RAM, and a 550Ti w/ 2GB of RAM. Should be more than enough to handle Darksiders even at 1920x1200 (the native res of my monitors). I couldn't even get decent performance at 1024x768, but I noticed these error messages about a temp swap file being made. So I go in, and sure enough, there's no swap file enabled on my system. I enable that, reboot, and now Darksiders runs nice n' smooth at 1920x1200.
So it might be worth a try to make sure there's a swap file enabled on your system, and I'd probably just let Windows manage it. It's free, it's fairly simple, and doesn't take too long, so even if it doesn't help, you're only out a little time and effort.