Win7 laptop shuts down unexpectedly (no blue screen) but Linux woks fine

I have a problem with my Toshiba Laptop (PinGuy 14.04 works fine but Win7 shuts down), it happens at random times: it could be just after logging in or while ruing some software after having the laptop on for a day or two, or even while idle.

It's important to say that it was working just fine for a year and half or even some more, and I don't recall installing anything new just before the problem started. I cleaned it inteally thinking it was a dust-related issue but it does not seem like it.

What could I check to make sure what is wrong?

Thanks