Amanda 2.5.1p1 packaged windows client is available for download at Zmanda downloads page - http://www.zmanda.com/downloads.html
Please take a look at the documentation for the Windows client package at Amanda wiki - http://wiki.zmanda.com/index.php/Windows_client
If you have questions, please post them in Amanda forums (http://forums.zmanda.com)
Thanks,
Paddy