Lockups, freezes and the 'blue screen of death'

If your computer freezes or locks-up, firstly try all of the above steps (see problem 1). If this doesn't help, then try updating your device drivers on the system. Check your computer's manual for instructions on how to do this if applicable. Also check to see whether your system is running low on disk-space or memory (RAM).
If none of the above help, your computer might have a hardware fault. A failing hard-drive could be one cause (a bad hard-drive will cause frequent lockups and freezes). In this case, contact your computer vendor (or the local repair shop if your computer's not under warranty) and go from there.