I was attempting to install the Windows Server 2003 Administration Pack on a server today, and unfortunately it failed with the following error:
The Windows Installer Service cannot update one or more protected files
After a bit of search on the web I learned that the source path was wrong on my server. Once I fixed the source path, I was able to successfully install the admin pack.
Use the following command-lines to update your source path to a network share:
reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup /v SourcePath /t REG_SZ /d \\ServerName\Share\W2k3SP1 /f
reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion" /v SourcePath /t REG_SZ /d \\ServerName\Share\W2k3SP1 /f