The HP LaserJet 1020 has drivers for Windows 98/ME/2000/XP.  Is there
anyway to install this printer onto an NT 4.0 machine?  Is there some
driver-emulation program I could use?

My suggestion is to use the HP LJ4 driver. Most HP Laserjet printers
(and many other non-HP Laser Jet printers) can emulate or understand
the HP LJ4 driver instructions set.

If you have success using that driver and it gives you all the
functionality you need leave it at that. However the LJ4 family of
drivers (e.g. LJ 4 Plus ...) may also be compatible so experimenting
with those wont hurt. Do however make sure you only have a couple of
sheets of paper in the printer as incorrect drivers can waste a lot of
paper printing out rubbish :-).

The Hewlett Packard LaserJet 1020 printer is a "Host Based Printer". 
This means the print jobs are processed on the computer and then sent
down to the computer.  The LaserJet 1020 printer is not compatible
with the LJ4 print drivers, so the previous suggestion will not work. 
Since it is host based you can only use the LJ 1020 print driver.

Host Based printers are not supported in the Windows NT 4.0
environment.  Also, this is a USB only printer, and Windows NT does
not support USB.  If you need to print from Windows NT, I would
suggest checking out the LaserJet 1320/1160 or LaserJet 2400 series
printers.

For additional information on Host Based printers checkout this link:
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=bpl07860