Flybywyre,
You are absolutely right regarding the 2 versions I mentioned - I should have made it clearer that in saying "with" a particular version I meant with an appropriately licensed copy!
Technically you can install multiple PCs from the same disk and with the same license key without any activation issues, - but this is with a Volume Licensing agreement, which few home users have!
It does seem peculiar to me that upgrading from XP Home to Pro costs the same as from Win98 to XP. Long gone are the days that upgrading from NT3.51 workstation to server required changing 2 or 3 registry keys (not that MS ever officially approved the upgrade)! AFAIR, it was not much harder to upgrade NT4 workstation to server either.
SD