I want to install DOS and Windows NT, how should I do this, and how should the hard disk be partitioned.

A. The best method is two create at least two partitions. The first around 200Mb and format to FAT, on this partition DOS will be installed. The reason 200Mb is suggested that this is enough space to later install Windows for Workgroups or Windows95 if needed. After installing DOS, install NT and install onto the second partition (and format FAT or NTFS). Once the installation is finished, on bootup of the machine you will have a choice of booting into DOS or NT. The advantage of having NT installed on a FAT partition is that if there is a problem then you can boot up in DOS mode and access the NT partition and possibly restore files, although that core NT startup files are located on the C partition anyway (boot.ini, ntdetect.com and ntldr).