For starters, the drivers and utilities for your Intel wireless card may need updating.
If you can't find updates for that, give us the model number of that wireless
card and maybe we can find it.

Try uninstalling as much of the Sony window dressing as you can. Only keep
what you actually use because factory installed software like that is usually
pretty weak and buggy.

Better check in at Windows Update to make sure you're patched up too.

In the meantime, go to the Setup menu in BearShare and in the Service tab
put a checkmark in "Never become an ultrapeer". That will temporarily stop
the disconnections, probably. ;]