An .msu file contains the following contents.
|Windows Update metadata||Describes each update package that the .msu contains|
|One or more .cab files ||Each .cab file represents one Windows update|
|An .xml file || |
This .xml file describes the .msu update package. Used for unattended installation of the update by using the Package Manager tool (Pkgmgr.exe).
|A properties file ||This file contains string properties that Wusa.exe uses. For example, this file contains the title of the associated article in the Microsoft Knowledge Base.|
To install an .msu update package, run Wusa.exe together with the full path of the file.
EG: if the Windows6.3-KB999777.msu file is in the C:\999777 folder, type the following command at a command prompt to install the update package:
- wusa.exe d:\999777\Windows6.3-KB999777.msu
If you want to expand it you can expand the .msu file to a temporary folder:
- expand -f:* "C:\999777\Windows6.3-KB999777.msu" %TEMP%
Then, you type the following command at a command prompt:
- pkgmgr.exe /n:%TEMP%\Windows6.3-KB999777.xml
OR if the package expands to a CAB file. You run the following commands to install the packages:
start /w Pkgmgr /ip /m:c:\temp\Windows6.3-KB999777-x86.cab
NOTE: Package Manager installs only the first cab found in a folder.
Source of this information: http://support.microsoft.com/kb/934307