My computer freezes or is behaving strangely

Try restarting your computer. Many basic problems can be resolved easily and quickly this way.
Press the Ctrl & Alt & Del keys on your keyboard together at the same time. This should bring up a menu that will allow you to run Task Manager. In Task Manager, switch to the Applications tab. Highlight any programs with the status 'Not Responding' and choose End Task. You may be asked to confirm if you want to end the unresponsive program, so choose Yes. Do this for all programs that are not responding.
If all else fails and you cannot shutdown/restart your computer, then hold down the power button on the machine until it forcibly turns off. Wait a few seconds and then turn it back on again.