El proceso vendría descrito en este articulo de la KB
Numbering scheme for product code GUIDs in Office 2003
En resumen, el proceso consisitiria en buscar desde regedit esta clave.
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall
Encontrarás una clave parecida a esta.
{WXYYZZZZ-6000-11D3-8CFE-0150048383C9}
W es el tipo de version y equivale a esto.
0 Any release before Beta 1
1 Beta 1
2 Beta 2
3 Release Candidate 0 (RC0)
4 Release Candidate 1 (RC1)/OEM Preview Release
5-8 Reserved values
9 Release to manufacturing. This is the first shipped version (initial
release).
A Service Pack 1 (SP1) (Unused if the product code is not changed after
release to manufacturing)
B Service Pack 2 (SP2) (Unused if the product code is not changed after
release to manufacturing)
C Service Pack 3 (SP3) (Unused if the product code is not changed after
release to manufacturing)
D-F Reserved values