Dell ABCD diagnostics lights

If you are having problems with your Dell pc, you might try taking a look on the back of it and you will notice 4 lights on the motherboard near the keyboard and mouse connections.  These 4 lights will give you an indication of what your problem might be.  It seems to vary between models as to what the lights mean but you can look up the problem either online or in the manual that came with the pc.  It should also give you a description of the beep codes.  Here is an example of the online documentation of a Dimension 4600.