You need to rescue the data from that pc and then install either Windows XP or at least Windows 2000. NT is way too old and I am not sure if Microsoft still supports it.
To get the data out, you could,
1. take the hard drive out of the box and then attach it to another pc as a slave drive. After that, you can copy whatever you need to another hard driver.
2. download a bootable CD image from here. burn it in a CD. Use the CD to boot that pc and then move the data somewhere else.