Hi! I have a mid 2011 macbook pro running os x yosemite on it. Yesterday when booting up my macbook pro I encountered the flashing question mark folder. So I did some research about it and tried some tips. When holding cmd+R I only get the option 'internet recovery' but it won't connect to my wifi even though i'm right next to the router. So I waited till I came home to try and boot from my snow leopard installation disc (the original one). This time the Apple logo came on with the loading circle and it stopped right there. I restarted the macbook and it gave the yosemite loading bar and everything worked fine again. This morning however, I needed once more to force my macbook to shut down (this seldomly occured until yesterday). So I tried again to boot from the installation disc but it's not working this time. Anyone knows what I might be dealing with? Thanks in advance!