Remote desktop is an option. Or a telnet session. Personally, I like using the remote desktop option, it lets me login to their computer from my workstation without losing their data. It works with both XP pro and Win2000pro. I never tried it with NT4.
I upgraded 90% of my workstations to XP pro for this very useful option.
All you need to do is download the Admin Pack from Microsoft. Works best with XP pro.