The samba suite for HP-UX comes as the CIFS/9000 software package on the HP-UX 11.x application CD's - or you can download it off the internet.
It is very easy to set up and administer, from what you have described the HP machine will be a CIFS server, sharing the directories on a disk with a NT machine - the reverse can also be done where you setup the HP machine to be a client so it can share directories on disks from NT (or UNIX) machines.
The documentation for both client and server applications is at:
http://www.hp.com/products1/unix/ope...documentation/
and is very easy to follow.
Regards.