I agree something is amiss but here are the most common reasons. Look at the pictures in the first supplied link and instpect your machine.

1. http://www.badcaps.net/
2. A machine with an aging power supply could do this as well. Many can't accept that 350 Watts is not enough or the unit decreases in capacity with time. I've written at length about this and will not do so as much. Your choice to look into this.

Bob