Dual Boot DOS + NT.

This really depends on if the hard drive is already partitioned, if you are able to partition it or if you have a second hard drive to use. If this is a fresh install I would first install dos in a partition and use that for the c: drive. Then create another partition or use a second hard drive to install windows NT on. NT should automatically update the bootloader for you. But if it doesn't, you can the either manually edit the boot.ini for both or use a third party program called bootparthttp://www.winimage.com/bootpart.htm
to do it for you.
If NT is already installed. For a description visit http://homepage.eircom.net/~davehernandez/multiboot.html
Just copy and paste the link into your browser.

If dos is already installed I would create a new partition and install NT to the new partition or second drive. The NT bootloader should recognize the dos partition and install the option for you on bootup. But ofcourse if it doesn't for some reason you can edit the boot.ini or use bootpart. This is really a very easy process and if you need any more help feel free to ask. I have dual and triple booted just about every operating system there is. With the exception of OS2. Maybe someday.