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