Hello and welcome to Bleepingcomputer.
When a computer freezes up, there are one of two issues that are causing it.
Issue number one. A bad driver.
Issue number two. Dust build up in the computer is causing internal hardware to over heat.
I would go with issue number two first.
In a lot of cases when a computer starts freezing up there is in most cases dust embedded in the heat sink fins preventing the heat from escaping.
The solution in this case is to open the computer up and check for dust in both the processor heat sink and the video card heat sink if it has one.
Check all cooling fans for signs of dust.
Dust acts like an insulator and prevents the heat sinks from distributing the heat into the air by way of the cooling fan.
You should use caution anytime you enter the inside of the computer case, your body has enough stored electrical energy to zap the sensitive electronics inside the computer case. To discharge this energy, you should first unplug the computer from the AC power, touch the computer case first, this equalizes your energy with the computers.
Inspect all heat sinks and cooling fans for dust.
Please click this link for further information.
If this does not help, you may need to see if there are newer more updated drivers available for your hardware, but I have a feeling dust is your major reason for the system freeze ups you are experiencing.