If you can't see the blue screen for more than a split second or the thing just reboots instantly, here's how to change it so you can see what it says:

Start-->right-click My Computer-->Properties
Advanced tab
Click "Settings" in the "Startup and Recovery" section
Uncheck the "Automatically Restart" box in the "System Failure" section

Then write it all down. Also, if you're really stuck, do this:

In the Startup and Recovery options page mentioned above, change the default drop-down from "Small memory dump (64k)" to Kernel or Complete.
Go into "C:\Windows" and find the file MEMORY.DMP
ZIP or RAR it down to manageable size.
Upload it to filefront or an FTP site somewhere.
Send us the link.

If you can get that far, someone can probably pull it and run it through Windbg and give you a better idea for what's failing. I can do a stack trace on it but suspect I won't be able to get all the way to root cause.