If your computer working normally before and this time you're experiencing hangup trouble probably there are problems on one of your hardware, either on video card goes on high temperature maybe lock of cooling, Due to failure of the cooling fan. Then also you can check your processor heatsink if it is tight on the processor using the thermal paste. Then clean-up all your hardware inside in your system unit, remove all dust build-up, and make sure that all the rotating fan working normally.
If all the things that I mentioned above are performed but still the hang-up has happened, concentrate on the software especially on the operating system. You can use the command mode of your computer. Use the command chkdsk /f/ r/x . Also check whether there are no viruses, update, and run your virus scanner. You can check also the health of your hard disk drive if it is not low. You can use Hard Disk Sentinel to check on it.
If this still not solve the problem you need a professional repairman to work on this technical work or bring your system unit in a service center near you.