If you're going to use the Unix machine as a server, it's probably not going to work to have a dual-boot system - you might want to have a dedicated machine for each one.
If it won't really be a server, but you still want a dual-boot machine, you should let us know what kind of Unix you're planning on installing. Each one wil be set up differently.
If you want a Unix environment on your NT machine (to practice...), you can try products such as Cygwin
http://www.cygwin.com/ .
Please let us know exactly what you need, and we'll try to help.
