Increase datastore size to 75 GB is it possible?

I currently have a Small Buisness 2003 Server running SP1. I know that I need to upgrade to SP2 and need to know if it is possible to increase the datastore size for exchange to 75 GB after upgrading to SP2 or am I limited to 16/17 GB b/c of the type of OS I am running on my server?

Any help greatly appreciated b/c my datastore is inching its way to 16 GB and need to find some answers quickly.