Q: MacBook Pro screen turns black and freezes

Every once in awhile when I'm doing something like browsing the internet or even using the photo booth, my screen blinks then immediately turns black. If there is audio playing, a split second of the audio loops over and over like an alarm (any audio, whether it's from a game, video or just music playing in the background) I can't do anything, because my mouse isn't there either. I have to force turn off the power and turn it back on, then a screen pops up saying "Your computer restarted because of a problem." I've tried looking up anything that could help, but I couldn't find anything. It just goes away after awhile and comes back at very inconvenient times.

My MacBook Pro is a 15 inch, mid 2010, and my OS X version is 10.11.3 (El Capitan). The memory is 8 GB. I did get a hard drive for this computer in December (which can hold up to 1000 GB), so I'm not sure if it's this hard drive that is making my computer crash like this.