OPENSTEP 4.2 Mach/Intel consists of the following

4.2_Install_disk.floppyimage (Bootable floppy)
4.2_Driver_Disk.floppyimage
OS42User.tgz - The User Install CD

You can install the following once OPENSTEP 4.2
has been successfully installed.

OS42Dev.tgz - Developer Tools
EOF21.tgz - Enterprise Object Framework 2.1 

Note: OS 4.2 Mach/Intel can be installed on Intel or AMD
based systems ONLY, 486 class or higher.

If you attempt to install this under Virtual PC, you
can assign a maximum of 32MB RAM to the virtual machine.
Why? I have no idea but it tends to make OS4.2 run horribly
slow. Check VPC Help and the Internet for other OPENSTEP
installation considerations.
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OPENSTEP 4.2 Enterprise for Windows NT:

OS42NT.tgz

This can only be installed on a Windows NT* based x86 system.
*Windows NT 4.0, WIndows 2000 Pro... Win XP will most
probably work, as well.

Alert: Neither OS4.2 Mach/Intel or the Enterprise Edition are
Y2k compliant out of the box. Look for Patch Release #4 (there
are several of them for the above components) and have them
handy on a CD for a quick install. Patch #4 for mach/Intel
also includes a VESA/VBE Video Driver that may be required
if the one you're using is not supported by the default install.

I'd recommend researching the Install process on the Internet
before actually attempting it.