That thing defaults to 50 which is probably good enough. If you ever see it
again try 100. BearShare and BT won't need more than that. It can go up to
16 million but there's no point because nothing can go that fast without
crashing your router. ;]

The fact that the newer BearShare worked makes sense. We were still using
Win9x and XP SP1 back when we were testing BS 4.5 and the changes to
accommodate XP SP2 didn't come along until many months later.

Now that it is working try the b25 version with BearStart. There are several
reasons to prefer it over any of the newer versions.