Sounds like you may be having a heat problem. There is no reason to let your computer sit and run and generate 125 fps, all you are doing is overheating your cpu and your video card both.
Hit the space bar and look under "Program settings" then check the limit frame rate box and set it to about 60 fps and give it a try then and see if this solves your problem.
As for the latest version, check
here. As long as you have a valid key code you can always download and install over what you have and end p with the latest version. If you don't have a internet connection with this system, then save it to something where you do have one and install it from disk.