I'm just guessing at some of this, but does the following sound about right?
XP retail version - (attended install).
The key in the PC will match the key label on the folio for the CD.
XP retail version - (unattended install)
The key in the PC will not match the key label on the folio for the CD, but will match the key located in the i386\unattended.txt file.
XP OEM version - (PC Mfg. Factory Install)
The key in the PC will not match the COA key labeled on the PC. This is due to unattended installation by the PC manufacturer using a Mfg. specific installation media or by cloning. But your license is the key located on that COA label.
However, the Mfg. may have adjusted the key to match the COA label prior to shipping. Or it may match in smaller scale operations where attended installation is done.
XP OEM recover CD - (PC Mfg. recovery CD, either sent w/PC or ordered later)
The key in the PC will most likely not match the COA key label on the PC & may not match the original OEM key either. This is due to CD's being burned and stocked in large but finite batches. Install may be attended or unattended and may or may not require a key. The required key may be included with the recovery media or you may have to use your COA key if asked for one. This will vary depending on the PC manufacturer.
User created recovery CD
Same as whatever method was used to do the install that the user created the recovery CD from. Keep track of your key, you may need it.
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