Dead Power Supply?

In an attempt to not sound completely inept, I would say up front that I'm 99% sure that I have a worn out power supply but I'm just looking for someone to confirm for me. The dead giveaway is that the system simply will not power up. One time I got the fan on the back of the supply to start spinning however the mb would not post. The only worrysome thing is that when this first happened and I unplugged everything and powered back up, the HDD light on the front of my case was blinking rapidly. I'm guessing that this could also be the result of not having quite enough power to bring the system online. By the way this was an Antec truepower 450 and is about 3 years old. I was under the impression that these things should last a little while longer than that.