You are in the process of installing some software package or a piece of hardware and suddenly the screen turns blue and you get an error message. These errors are generally caused by some driver or bad piece of hardware. In most cases it's a driver that goes with some item of hardware that won't work and play well with other stuff in your computer. In other cases it's that the system is busy attempting to do something and is stuck in a loop or just crashed or maybe it's trying to read a CD ROM or floppy disk that has been removed from the drive before Windows has a chance to close it. This is generally an error that will bring down your system and gives you no choice but to cold boot the system. The error message will also display information about the error and register information, copy this info down, it will help direct the Tech to the nature of the problem. Whatever caused the blue screen will need to be corrected before you can proceed using the computer. Removable of the offending item or software will usually fix the problem, however in some cases you will need to restore the last know good registry file and then reboot. It's always a good idea to create a backup of your registry before attempting to install software or hardware, this way if the installation fails for any reason, you can restore your registry returning the system back to it's condition before the failure. For blue screens that occur during normal use of the system, it would be best to contact your computer service provider.