I have Windows 7 (from today) and I suprised, why can not connect to the samba linux box. Everything works fine for a Windows Vista and a samba. Fast research and got Win7_Samba3DomainMember from wiki samba. Just what you have to do :
https://bugzilla.samba.org/attachment.cgi?id=4988&action=view
and run this on your Windows 7 box.