GLM with Random Factors

#1
Hi:

Newbie to SPSS. Tons of stats and programming knowledge ... but helping a novice with their SPSS work.

We're doing a GLM with a random factor. When I put a factor in (incorrectly) as fixed I get one less piece of output, and when I put the factor in (correctly) as random I'd like to know why I'm getting that extra output.

The output in question is the table labeled "Expected Mean Squares". Why is this produced? Is this so I have available to me some corrected values that I might use in the calculation of other statistics?

Is there a primer somewhere on using this information?