If you experience a blue screen on your computer, it is because your computer has crashed. The blue screen of death, or BSOD, as it is commonly known, can occur for any number of reasons, including running too many programs or running conflicting programs or from failing hardware. Updating Windows could remedy most of these if it is not a hardware issue; however, in the event that it doesn’t, you may experience further issues with your Windows XP installation. In that case, you can reinstall Windows if you have the installation disc or a recovery partition.

Instructions

Put your computer in safe mode by turning it on, tapping F8 immediately and selecting “Safe Mode.”
Back up any important data once your computer has started.
Put your Windows installation disc in the drive, while you are at the blue screen.
Turn the computer off using the power button.
Restart the computer and start tapping F12, which will bring you to the “Boot Menu.”
Select boot from CD or DVD, which will allow you to boot from your Windows XP installation disc.
Follow on screen instructions to re-install your windows O.S