in fact, that is the default behaviour (well, at least it has always been for me)
to change that you can do this (win2000/XP; it's slightly different under win98):
open windows explorer
tools-->folder options
file types
select the avi file type (of course you'll have to repeat with every file type that behaves like that)
click advanced
if there is already a "play with bsplayer" item or like, edit it
in the "application used to perform this action" field, you should have
Code:
"C:\Program Files\bsplayer\bplay.exe" "%L"
if there is no "play with bsplayer" item, create it and put the above command line
validate the item edition
then select the item and click "set default"
validate etc...
Note: the "enqueue in bsplayer" item has the following command line:
Code:
"C:\Program Files\bsplayer\bplay.exe" "%L" -ADD