Did the installation of the service pack fail? If so, I agree with Ed. Download a new set of installation media.
If the SP installation succeeded, and there are missing .msi files, the first try to install the previous service pack, and then re-install the new one.
Otherwise, you may have to do a repair of your installation.
There used to be a file checker for Visual Studio. I don't think I've ever seen one for SQL.
Michael L John
If you assassinate a DBA, would you pull a trigger?
To properly post on a forum:
http://www.sqlservercentral.com/articles/61537/