Your PC Freeze due to following reason:
1)Malicious Programs
Malicious programs such as viruses, Trojans, spyware and worms have the ability to secretly install on a computer system and delete vital system files, infect programs and cause your computer to freeze when you attempt to launch or use applications They also have the ability to hijack browsers and adjust start-up functions and as a result cause your computer to eventually crash. Since some of these malicious files have the ability to duplicate themselves, they can overpower your computer system and prevent you from using it.
2)Compatibility issues
Installing a program on a computer that does not have the necessary hardware and system resources to handle it can not only cause your computer to slow down but also cause the program to continually freeze. Many large media programs, for example, require large amounts of system RAM and processor speed. They will run into many errors if they are installed on a computer with insufficient resources. Before installing programs, it is important to always check the system requirements to see if your computer meets them.
3)Registry Problems
The registry is a large database that contains the settings and configurations necessary to run programs, applications and system components on your computer. It can be adversely affected by uninstalled programs that leave entries in it. It can also become corrupt due to improper computer management and as a result cause system errors which cause programs and system components to freeze. Because the registry is used every time you install or uninstall a program, its performance is vital to how the rest of the computer performs.
4)Solution
If a specific program keeps freezing, uninstall it and try reinstalling it again. You should run frequent virus scans to detect and remove malicious files. If you do not have an antivirus program, consider a free antivirus program such as AVG (see References). Avoid installing applications that your computer does not have adequate hardware for. If an application requires a minimum of 1GB of RAM and your computer only has 128MB of RAM, it's probably not a good idea to install it on your computer. Run a registry cleaner program such as CCleaner (see References) to remove unnecessary registry files.