So, I get home from class and go on my MacBook. I noticed everything was running very sluggish and certain applications weren't responding. I try to force quit the applications but that didn't work. I then unplug my Mac and take the battery out and wait a few minutes then put it back in. I turn it on and it gives me the white screen with the Apple logo for a few minutes. I then repeat the process and try again and the same thing happens. The 3rd try I get the same thing but then after a few minutes the Apple logo goes away and turns into a circle with a slash through it. I've never seen this before and I'm getting somewhat worried. I recently got a new HD so i'm not sure if thats got anything to do with it.