Whether an effect is fixed or random is not a property of the HLM software but rather of your model. A fixed effect is one that no matter how many samples you take the same values are possible for this variable {e.g. "Yes", "No"}. A random effect is one where the variable's values in your sample data comprise a subset of all of those values possible.

see:

http://stats.stackexchange.com/questions/4700/what-is-the-difference-between-fixed-effect-random-effect-and-mixed-effect-mode