It seems to me that the problem could be one of hardware. If the CPU was running at 3 GHz and now it shows as 1GHz, then the CPU was overclocked. In cases like this problems can arise if gthe CPU is overheating. It is summertime, so at this time of the year computers can overheat. It is possible taht the graphics card might be overheating too. I have a computer program that runs from DOS. It can test all your hardware for potential problems. If you send me your e-mail in a private message, I will send the program to you. Then you can scan your PC.

After eliminating the hardware problem, then the next step is to make sure that the BIOS of your computer is the latest version. For that you will need to know who the manufacturer of the motherboard is so you can go to their website and download the latest BIOS version. Then you can flash the BIOS into the BIOS ROM. If you have the manual for the PC, it will tell you what motherboard you have. If you don't have the manual you can also open the computer and look at the manufacturer and the model number of your motherboard. If you don't want to open the computer have another small program that will read the BIOS and tell you the motherboard manufacturer and model. After that you can update the BIOS with the utilities that the manufacturer provides.

Well, let me know if you want the programs, I am sure they can help at least to diagnose any potential problems. One more question, is the computer crashing only when playing games, or when doing other tasks? If it is doing it only when playing games you can also install the latest version of Direct X from the Microsoft website. Direct X tends to interact directly with the graphics card GPU, and if Direct X is causing a problem because of a bug then the latest version can help too.