"already have migrated"
There are lots of reasons why you may want/need to keep an old OS going, the most obvious is you simply don't have the money to buy a new PC but that is probably not the biggest issue here (though report suggested so).
Legacy software, or special hardware, are both reasons why an 'upgrade' can be very expensive and time consuming because you find that the software won't work right on the new OS and/or is not supported or licensable on a new machine, and newer versions of said software is not 100% backward compatible and/or needs something else and so on...
My own solution for my dying w2k box was to convert it into a VM and run it on a Linux machine, more or less the best of both worlds (can run special software that is Windows-only, has better network security Linux-style). Even so, that takes IT skill to implement and user training to make it workable, both of which also cost money one way or another.
Certainly w2k and XP had nothing in the license about virtulisation, but AFAIK Windows 7 (probably also the abomination that was Vista) only permit it on the expensive enterprise version, not OEM/standard.