What are you doing when the system crashes (this is the infamous Blue Screen of Death - aka BSoD)?
What are the detailed specifications of your system?
What have you done recently to your system (added, removed, updated, etc)?
Is there anything that sticks out in your mind that may be significant?
Also, locate the minidump file for the crashes (usually in the C:\Windows\Minidump folder), zip them up, then upload the .zip file in your next post.
We'll have a look at them to see if they tell us anything significant.