Computer freezing is usually a problem with the Windows registry. The registry is a large database in Windows that has all the needed configuration information for all Windows settings, all applications installed in Windows, and all hardware devices installed. If you have recently installed either new software or hardware you might return the computer to a previous restore point and see if that corrects the problem. If not it could be a number of other things, such as, more RAM needed, hard drive full, hard drive corrupted or fragmented, RAM memory errors, virus, or malware infections. I have another HubPage concerning Slow Computer that might help correct some of the problems.  You might also checkout this YouTube video Reboot Computer: