I came across this error message below while installing Exchange 2007 SP3 (vanilla install) on a Windows 2008 R2 SP1 server.
Microsoft has released update rollup 8 for Exchange 2007 SP3 deployments.
In addition to UR2 for Exchange 2010 SP2, Microsoft has released Update Rollup 7 for Exchange 2010 SP3 servers.
Microsoft has released update rollup 6 for Exchange 2007 SP3 deployments. For a list of changes that are included in this update rollup, see KB2608656.