XP Home User Limit

I am using XP Home SP2 on a small office network of 6 computers. We have 3 mapped drives set up on our “server” for our data files but are having problems with gaining access. From what I have read it appears we have max. 10 connections; thus we consistantly need to log someone off from one mapped drives to open up another connection access. (It looks like each mapped drive makes a seperate connection, so some computers actually take up two or three connections if logged on to the various mapped drives.)

Is there anyway to increase number of allowed users on XP Home? If we upgrade our server to XP Pro or Vista, do we run into issue of max users allowed?