Unstable

My desktop computer is unstable again. I think it's my hard drive. But my desktop is on the fritz again, giving me massive blue screens of death. I've toyed with the RAM. A friend suggested that it might be the hard drive. I refused to believe, until I finally noticed that sometimes the damn thing wouldn't access the hard drive. It just wasn't thinking. I hope that that's all... because I'm going to go ape shit if I buy a new hard drive and that isn't the problem! That makes 2 hard drives I have to buy... 1 for my laptop and the other for the desktop. Massive le sigh.