Did you see http://makemsi-manual.dennisbareis.com/using_orca_and_msidiff_to_automat...
There are some other tools available for MSI changes as well, but if you want to use Orca you don't need the full SDK install on the build engine, just copy and use orca.exe on the build engine and automate using the information on the above link.
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RE: Automate VS2005->VS2008 Target Change?
Did you see http://makemsi-manual.dennisbareis.com/using_orca_and_msidiff_to_automat...
There are some other tools available for MSI changes as well, but if you want to use Orca you don't need the full SDK install on the build engine, just copy and use orca.exe on the build engine and automate using the information on the above link.