When installing SQL Server 2008 Service Pack 3 related updates, some don’t like compressed directories (even if the database files themselves are uncompressed).
I found this holds at least for KB2977321 and KB2285068.
For x86 systems, ensure these directories are not compressed:
C:\Program Files\Microsoft SQL Server
C:\Program Files\Microsoft SQL Server Compact Edition
For x64 systems, ensure these directories are not compressed:
C:\Program Files\Microsoft SQL Server
C:\Program Files x86\Microsoft SQL Server
C:\Program Files x86\Microsoft SQL Server Compact Edition
–jeroen
via: Can not install KB2285068 Error Code 84B40000 – Microsoft Community.