Windows XP build 2537

Windows XP build 2537 is mentioned in the Windows XP Service Pack 1 source code in the file :

It is used as a default version if the build for the MAPISTUB component is not set, and was likely taken from the current build at the time.
 * 1) define VER_FILEVERSION                5,5,2537,VER_PRODUCTBUILD_QFE

Build 2538 is also mentioned in the same file.