When you boot your system and you are greeted with a blue screen (BSOD), you are usually pretty helpless. The cause of the blue screen could be software or hardware related. The same applies when you get constant BSODs during normal operation.
To rule out possible hardware problems (defective RAM, Disk, Mobo, Graphics card, etc.), my first course of action is to load a Linux distro from a USB stick or CD. If Linux loads and runs properly, you can assume that the hardware is OK.
You need not be a Linux expert to do that. You only need to play around with the different icons and buttons on the Linux screen to see whether it operates normally.
I use Fedora on a USB stick. The instructions on how to make such a stick you find here: http://lifehacker.com/391067/fedora-9-puts-your-desktop-on-a-usb-drive
But there are many other Linux distros that you can download and burn to CD – e.g. from here: http://unetbootin.sourceforge.net/
Once you made sure your hardware works properly, then you can go and search for the problem in Windows – which is usually not an easy task.