Hi BRL,
Not sure if this is your problem - but if the task bar is also twice as high as normal; I would think that you do not have the task bar locked!
Right click the task bar - if task bar is locked there will be a tick against that item in the list. - If no tick it is indeed unlocked..
so when unlocked - move cursor to top edge of task bar until small double headed black arrow appears and then left click and hold button down whilst dragging the task bar down to make smaller and then release..
then right click task bar again and select tick task bar locked and it will not reoccur.
Hope that helps!
PS that works in XP - not sure what O/S you're using?