List all components.
Explain the error/problem in as much detail as possible. (Unless already done so)
Write down the exact and full Bluescreen message and post in next reply.
When did this error start to occur?
Have you made any software or hardware additions prior to this problem?
If they is anything else that you want to add or find unusual about the problem please tell.
First thing to try is a repair from your windows OS Disc.
Its also a good idea to back up all important information first by plugging the drive into another computer, as Slave.