Here is how you can find out the edition: Enterprise/Standard/Branch
HKLM\SOFTWARE\Microsoft\BizTalk Server\3.0 and the key ProductEdition. This should tell you if it is Enterprise/Standard or Branch....
BizTalk version through Registry:
BizTalk Server 2004
BizTalk Server 2004 SP1
BizTalk Server 2004 SP2
BizTalk Server 2006
BizTalk Server 2006 R2
Here is a way to determine the version of BizTalk Server through Database:
open BizTalkDBVersion Table from BizTalk Management database.. Do not change any values here as the supportability clause comes into picture....
Version(Minor + Major)
BizTalk 2006 R2
BizTalk 2006 RTM
BizTalk 2004 SP2
If table exists ('admv__BackupDatabases')
BizTalk 2004 SP1
If table exists ('adm_OtherDatabases')
BizTalk 2004 RTM
If not table specified above exist
This is by DB version though.. not the registry.. there should be some easy way to tell, trying to get that mapping...