You must read the message regarding software licenses in Section 1.6 before you install Windows NT 4.0 as a guest operating system in Bochs.
Here are the known issues about installing and running Windows NT4.0 :
If you want to use the LGPL'd VGABIOS to install Windows NT 4.0 you'll need version 0.4c or higher. With older versions you'll get a black screen after first reboot.
to log in you must press ctrl-alt-del, and it is likely that the window manager will trap this key combination. You can either use the trick described in Section 9.17 or define a user short-cut (callable through the user short-cut gui button) in you configuration file, for example:
keyboard: user_shortcut=ctrl-alt-del
For installing and using Windows NT it is necessary to limit the maximum CPUID to 3. In the configuration file you need to add a line like this:
cpuid: cpuid_limit_winnt=1