The short answer is MAYBE! BSOD can be caused by any number of issues-many of them hardware related. If your machine is still under warranty I would contact the Manufacturer. If it is not, then you need to find the cause of the BSOD events--could be a bad RAM stick, malware, viruses etc. I would consider taking it to a reputable repair facility, and let them diagnose it--most respectable shops offer this service for free, the repairs of course are not free.
You don't have to buy new W7 copy to reinstall it you just need to get the code (it should be on a tape on the pc or laptop) and just get the W7 from another pc but be sure it's the same kind like home premium or ultimate but I don't really know if it will solve the blue screen it may be your hardware not software check your GPU drivers and update them and do some researches before you reinstall W7
All of the OEM products are on a partition on the hard drive usually designated as "D". You will lose all your data files that you've done unless backed up. You can do a system retire back to the new level.