Accompanying the blue screen there is usually an error message. If your system reboots before the message is displayed then you need to turn off the automatic restart in your system settings.
There are many possible causes for a bluescreen and without the error message we have no way of advising what direction you should proceed.
The other possibility is a can of blue spraypaint exploded in front of your PC. If this is your problem then wipe it off before it dries.
Goin' Fishin' (Some day)
There are many causes for the Blue Screen to occur. Some of them are the loose memory chip from its slot, or it may have been gone bad, your computer's Hard-Disk may have become corrupted. So if you want to know the exact cause of the Blue Screen then write its "Error Code" so that it can be said clearly about its cause. Solving Technical queries is my passion and I just Love it !!
blue screen shows in flash 1/10th second, no one can read error after that system show xp booting wait 18,17,16,...again restart i change RAm, SMPS,Bus,even hard disk but dnt get solution....dear