After far too long, I got this "rebuilt" installation of Windows XP Home to boot and let me fix it.

A friend's PC died; mainboard failed. We replaced the faulty part, with its own adventures, and found that his installation of Windows XP Home that worked before the board failure didn't work so well.

I got XP to boot by running through the "repair" on the install disk. It rediscovered the hardware, which is probably what kept it from booting correctly, and would now boot to the "welcome" screen. When choosing a user, however, a message box would appear warning that Windows needed to be activated. Fine; I expected that as the hardware had drastically changed. However, once inside the user session, the activation wizard would state that Windows was already activated. Clicking the presented "OK" button, or closing the window by any other method, would log the user out. Repeat. Repeat. Repeat...

I found and tried many solutions on the Internet, but no success.

Eventually I tried "upgrading" the system to Windows XP Home. When booting off the CD, the only options were to "repair" or "replace" the current installation. I didn't see any use in letting Windows forget about all of the other installed software, or risking any data that the install might remove. I booted in "safe mode" and tried running the setup from within Windows.

It tried to tell me another setup program had not finished. I suppose it was the "repair." I dug in the registry and removed the "RunOnce" items, which I saved for replacing later if needed. I retried, and success was mine.

Two hours of copying later, the installation demanded that I activate Windows, but this time offered me the correct information. A few minutes on the toll-free with Microsoft's automated activation wizard, and everything was up and running.

On to the updates...