Play Detective and look for clues...
The most difficult part of troubleshooting a computer is to find out what actually has happened or what is going on right now.
I know it sounds crazy...you were standing right there when the dang computer went on the fritz. You know what happened, right?
What you saw was a "symptom". And, like a doctor diagnosing an illness, a symptom is simply a sign or indicator of what is really going bad in the background.
Getting a symptom description (looking for a pattern) is simply a way for you to understand what is really happening to your machine. You should always document every error message and note what programs were open when the problem occurred, even the time of day!
I'm not kidding with that last idea. I saw one computer once that only acted strange after lunch! It was in a very hot, poorly vented office and would routinely overheat in the afternoons.
Get it down on paper because you will forget all the details! (Trust me on this one). Detail any error messages you see. The "Blue Screen of Death" will have a message explaining what is going wrong. Break out your pencil and write this stuff down.
I know you want to fix all your problems as soon as possible, but if worst comes to worst, you may have to take your machine to the repair shop and you will have to share what you have seen or done with your tech support person.
So stop being such a slacker, and write down it!