Using the registry, determine what version/service pack of LCS or OCS is installed

Check this registry setting:

HKLM\Software\Microsoft\Real-Time Communications\{92AC8981-AAD9-4391-8563-92E558EEF4C6}\Server
SE - Standard Edition
EE - Enterprise Edition

HKLM\Software\Microsoft\Real-Time Communications\{92AC8981-AAD9-4391-8563-92E558EEF4C6}\Type
Volume - volume license edition
Eval - evaluation edition and/or beta
MSDN - MSDN edition

HKLM\Software\Microsoft\Real-Time Communications\{92AC8981-AAD9-4391-8563-92E558EEF4C6}\Version
1.0.4949.0 - Live Communications Server 2003 RTM
2.0.5369.0 - Live Communications Server 2005 RTM
2.0.5470.0 - Live Communications Server 2005 SP1
3.0.6090.0 - Office Communications Server 2007 Beta 3
3.0.6362.0 - Office Communications Server 2007 RTM