How To Keep Your PC From Freezing
First thing to do is go to Start, go to Control Panel and click on Windows Updates. Download any updates from Microsoft. This is a good place to start as Microsoft makes patches all the time to fix known bugs with their software.
You may not have enough memory in your system. This is another possibility. Go to Start, go to Control Panel and click on System. Under the General tab look at Computer and analyze your power. If your memory is under 1 GB of RAM, you may need to upgrade to 1 GB or higher by buying new RAM and installing into the computer.
You may have a hardware driver issue. You can update your drivers manually or by using Driver Detective you can check all drivers and update them. Get all the latest drivers for your hardware, this is very important. Include any PCI cards and external devices.
Check for BIOS updates for your motherboard.
Check your hard drive, it could be overworked. Clear out any old or bulky files and then use Disk Defragmenter.