My MAc Book pro Has started running extemely slowly

. I have tried to trouble shoot with no result. It does not seem to be internet related. But films and all applications take minutes to open and the beach ball keeps coming up.

I have OS X Yosemite 10.10.2. 15 inch Macbook pro 2011. 4GB memory. 2 GHz intel Core i7,

Safari 8.0.4, Iphoto 9.0.6