that depends on 'where' Backtrack and Windows are.
For instance, if Backtrack is in a VirtualBox VM you can setup a 'folder share' and simply copy files on backtrack into the share which will then appear on your Windows filesystem
basically it works in the same way as a 'network share'
for network, I think you can use rsync,
https://en.wikipedia.org/wiki/Rsync
as well as mounting a windows share in backtrack
