"Once in a while a Linux PC technician will encounter a system that has problems with lockups (a.k.a. hanging or freezing). Sometimes it is failing hardware but other times it's a software problem. Here are the common causes for this and how to identify which is the source of your problems. While I predominantly use Ubuntu (and some Mandriva) these tests are valid for most any distribution.
"1. A kernel crash or panic is rare but generally fatal. As any PC tech knows, the first test is seeing if the Caps Lock, Num Lock, or Scroll Lock LEDs change state when the corresponding keys are pressed as this is performed by the PC, not the keyboard controller. If they don't change then you know you've got a freeze problem. If the keyboard lights are flashing repeatedly during the freeze then it's a panic. More severe problems can prevent the kernel from failing gracefully enough to even do that. These failures can be caused by fundamental compatibility problems with a kernel module and a critical piece of hardware (like a BIOS with a broken ACPI implementation), a device that was given commands it didn't like and has stopped responding (like a video GPU) or just failing hardware (bad RAM, overheating CPU, and loose PCI or AGP cards).
"With hardware problems it is best to start by opening the case and blowing the dust out since that is the source of most overheating problems. After cleaning a few systems you'll understand why you should charge extra for smokers, pet owners, and homes with shag carpet. I find it easiest to use an air compressor with a tank and a blow-off nozzle to do the job as canned air is too weak."
