A "blue screen" or "blue screen of death" (bsod) can be cause by many many different things.. if the computer is only 18 months old, it is less likely to be a hardware issue although still possible. That being said, I would try to cover all the software issues first.
Typically when I work on computers that are getting the BSOD, I make sure they have all the latest windows updates and also all the latest drivers from the manufacturer's website. Often times the manufacturer will release an update that fixes these sorts of issues. I would hope that if you took it to a computer shop multiple times, they would have done this, but you never know.
Unfortunately you didn't give us very much information to work with so it will be very hard to diagnose your problem further. Try checking the manufacturer's website to see if you have all of the latest drivers and updates, and make sure your windows updates are all caught up. Also, if there is any information on the blue screen that you can write down, that would help too!