At a guess I'd suspect the graphics card, motherboard, power supply or even the hard drive.
Is your computer still under warranty? If so you need to talk to Dell about the problem.
One of my computers is the same model as yours and I had the motherboard replaced under warranty for exactly the same problem that you are experiencing.
At the very least you should check to see that your motherboard components such as the graphics card and RAM modules are seated correctly.
While you've got the box open you can always carefully shift any dust with a can of compressed air.
One possible solution I've read about involved switching your computer off then disconnecting the card reader power cable and grounding it to earth to discharge any power stored on it then reconnecting it.
I also remember reading that leaving a card plugged into the reader can cause problems during startup. http://supportfordell.iyogi.com/inspiron-545/error-code-2.html
You might also want to run the Dell Diagnostics utility to see if you have a hardware problem. http://support.dell.com/support/topi...&isLegacy=true