We have had a number of customers specify the Hummingbird products when they know they will be accessing their Unix systems from our NT systems - they seem to have a good reputation.

You could also opt for a low cost solution like WS_FTP® Pro 6.0 $37.50, which runs on any Win platform. I use it a lot and it integrates right into Windows Explorer or you can use its native interface. Get it online from the author at http://www.ipswitch.com