Is your organization more than 9 years behind on your network-migration strategy? Are you still relying upon Windows...
NT 3.51? Have you finally made the decision to upgrade to Windows 2000 Server or Windows Server 2003? If so, I'm glad I'm not in your position.
The prospect of upgrading through two or three major Windows Server revisions is quite daunting. If you can, I'd suggest scrapping everything and starting over from scratch. The only thing I'd consider re-using from such an ancient network might be the mouse pads.
However, you may have to stick with the bulk of your existing systems, but need to perform an upgrade. Well, there are several hurdles you must successfully overcome on your way toward your goal of a more modern network system.
Most of the hardware present during the hey day of Windows NT 3.51 is not even supported by Windows 2000 Server, much less Windows Server 2003. If you are fortunate enough to have Pentium systems rather than 486s, then your hardware replacement needs are minimized. Make sure you thoroughly review the minimum hardware requirements and compare them with your current infrastructure. I'd even use the hardware compatibility verification tool off of the 2000/2003 CD to test each system.
Another problem is that most of your applications may not be supported by the modern Windows NOSes. NT 3.51 applications used different means to store configuration and operational information than modern versions.
To minimize the negative aspects of these issues, try a stepped upgrade process rather than a full bore leap. Upgrade the network first to Windows NT 4.0. Once all of your systems and applications are working properly, then take the next step to Windows 2000. Then if desired, move on up to Windows 2003. With this type of migration, you'll be able incrementally to upgrade aspects of the network (hardware and software). At each step along the way, you'll be able verify that your data and overall network operations are still supported and accessible.
I would strictly avoid retaining any Windows NT 3.51 systems once you have deployed a Windows 2000 Server system. There are several key differences with the way these two systems authenticate users, build access tokens, and manage SIDs. Windows NT 4.0, Windows 2000, and Windows 2003 don't have these compatibility issues. So, if you can only migrate some systems to Windows NT 4.0, you'll still be able to upgrade the others to 2000 or 2003.
James Michael Stewart is a partner and researcher for Itinfopros, a technology-focused writing and training organization.