Howto strip off Domain Name

Hello there, I managed to get FreeRadius authenticating users with PEAP against a OpenLDAP Directory containing my Samba controlled domain data and users. The Users are stored with der normal username (without Domain) in the LDAP. As default the windows WLAN Client tries to authenticate with the entered windows logon credentials which is fine if the client would send the username without the Domain added. When FreeRadius looks up DOMAIN\testuser in the LDAP there is obviously no result because the user is stored as testuser. So what can I do to strip of any Domain Name by default? Thanks in Advance, Sebastian Mauer