I had to support Win NT 4.0 sp6a up until the bitter end along with still very active Win 9x machines. The reason was due to some legacy applications that required that environment.
Finally in 2007 we upgraded to Vista Business. It was actually the best version of Vista out there, and I was able to setup any legacy applications to run in virtual machines. We used Parallels for the VMs and they ran pretty well. It took a lot of convincing of the upper management to break away from the old technology, and this happened only after a critical machine died and we had no choice but to upgrade.
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