Computer freezes is usually related to hardware, meaning the video card, random access memory (RAM), or another component may be underperforming. Software also can lead to a frozen computer, as can issues with drivers, the operating system, and malware;
A virus or spyware infection on your computer might also be the source of freeze issues.all these things can stop a computer from working properly.
1.If the freeze happens every time a certain hardware device is plugged in or switched on, the device itself might be to blame. Check drivers update for the device, and download and install them to erase any bugs that might exist in your version. Similarly, if the freeze only happens when using one particular application, that program might also be the root cause.
2.Run the System Restore utility from the System Tools section of the Accessories folder on the Start menu to roll back Windows to a previous version of the registry. This will fix prior registry issues without affecting personal files and settings.
3.If your computer still keeps freezing up after you take the solutions above, I suggest you to download a software to deal with it. The choice is sure to be more effective and simple, but there are few free utilities for this issue. Windows Boot Genius
is a excellent one if you wanna take this solution. source:http://windows-repair.net/computer-freezes.html