Yes more info is needed. Freezes can be caused by a unlimited amount of things, bad memory, bad sectors on the hard drive, bad video, bad hardware period, bad drivers, 3rd party programs, corrupt registry and so on.
So the trick is to do a process of elimination.
1. Make sure it isnt a 3rd party program or antivirus. Do a clean boot, which means all 3rd party programs should be disabled from startup. Which you should see the system will normally be a lot faster since it wont have all the background programs running. If the problem goes away then you know it is one of the 3rd party programs causing the trouble.
2. Test the memory, there are memory tester you can use, Windows even has on, where you can test the memory and make sure it is good.
3. Do a chkdsk on the drive and have it look for bad sectors.
4. If all the above check out fine and you still have the problem then try safe mode with networking for a while and see how it does. safe mode loads with only the default drivers needed to run, and so if ity works fine there it is either a driver causing the problem or a 3rd party program. It can be a 3rd party program because some of them install drivers of their own, like the anti virus does.
Shane