i was poking around and found this little goodie...
IsOS API Function
http://msdn.microsoft.com/en-us/library/bb773795%28v=vs.85%29.aspx
of particular interest to me is the index OS_WOW6432
but, here's the complete list...
OS_WINDOWS EQU 0
OS_NT EQU 1
OS_WIN95ORGREATER EQU 2
OS_NT4ORGREATER EQU 3
OS_WIN98ORGREATER EQU 5
OS_WIN98_GOLD EQU 6
OS_WIN2000ORGREATER EQU 7
OS_WIN2000PRO EQU 8
OS_WIN2000SERVER EQU 9
OS_WIN2000ADVSERVER EQU 10
OS_WIN2000DATACENTER EQU 11
OS_WIN2000TERMINAL EQU 12
OS_EMBEDDED EQU 13
OS_TERMINALCLIENT EQU 14
OS_TERMINALREMOTEADMIN EQU 15
OS_WIN95_GOLD EQU 16
OS_MEORGREATER EQU 17
OS_XPORGREATER EQU 18
OS_HOME EQU 19
OS_PROFESSIONAL EQU 20
OS_DATACENTER EQU 21
OS_ADVSERVER EQU 22
OS_SERVER EQU 23
OS_TERMINALSERVER EQU 24
OS_PERSONALTERMINALSERVER EQU 25
OS_FASTUSERSWITCHING EQU 26
OS_WELCOMELOGONUI EQU 27
OS_DOMAINMEMBER EQU 28
OS_ANYSERVER EQU 29
OS_WOW6432 EQU 30
OS_WEBSERVER EQU 31
OS_SMALLBUSINESSSERVER EQU 32
OS_TABLETPC EQU 33
OS_SERVERADMINUI EQU 34
OS_MEDIACENTER EQU 35
OS_APPLIANCE EQU 36