Judging by the fact that XP SP 3 Release Candidate 2 Refresh 2 was Build 5508, speculation began circulating of a new version number 5573, that could even be the RTM build for the service pack. Softpedia contacted Microsoft on the matter, and this is not the case.
"The reference comes from 'A multiprocessor computer that is running Windows Vista or Windows XP stops responding on a black screen after you resume the computer from hibernation' KB article 951126 available here: http://support.microsoft.com/kb/951126/. The file versions discussed on the Microsoft Help and Support page, referring to a hotfix for Windows XP SP3, are accurate," a Microsoft spokesman revealed in an email to Softpedia.
Yes, 5573 is mentioned alongside the hotfix for XP SP3, but this does not mean that it is also the gold build of the service pack. "The high numbering is common practice for hotfixes that are intended to be able to be applied to multiple versions of the operating system. The file version discussed does not imply a specific Windows XP SP3 version number," the spokesman added.
Microsoft, Windows XP, SP3, XP SP3, RTM, Build 5573