Digital BW, The Print

Sorry gang but I'm desperate. Quick photoshop question.

Somehow my history window is limiting the number of actions it will
register to 20 or so. Isn't there a quick way to set it to 99 or
something? I just can't figure out how to do it and I'm in the middle
of something important. 

Anyone know how to reset this and perhaps explain why it changed in
the first place?

Thanks,

Tim