CPU Problems, am I dead?

I have a dell dimension e510 which had been working fine for over a year. Yesterday when I started it, it did not make it past the bios screen and emitted a continuos beep. I found out a bit about bios beep codes and re-seated all video and memory cards, but nothing changed. I removed all memory cards and put one back, and it worked. I then added a second card, and again it worked. I added a third and it stopped working, but once I removed the third and tried again, it would not work. Now it will not work with any of the memory cards in. Are my cards shot? Or my cards slots? Any help would be appreciated.

a_dark_vision, your motherboard or power supply may have failed. The power supply voltages can be measured at the motherboard connector with a DVM (Digital Volt Meter). Also, be certain that you always unplug the power cord and ground yourself before reseating or swapping static sensitive components.

Comp