Windows xp one computer one cd(license) really work

You’ve got a few different questions there, so let’s see if we can simplify this a bit.

1) When you install Windows XP on a PC, it create a record for itself of the hardware within that PC, along with activating Windows. That hardware record can be modified by making some changes to the hardware over time (something like adding a video card or a hard drive).

2) If you reformat and reinstall a copy of Windows that requires activation, if you do it more than once in 120 days, you will not be able to activate it over the internet, and will have to call Microsoft at the appropriate phone number from the list provided through the activation window.

3) If you purchased a copy of Windows XP to install on a PC and you later want/have to replace the PC with a new one, and the new PC does not have Windows, the conditions in point (2) apply.