Adding Windows Vista features takes an extended period of time or may stop with an error message
On Windows Vista Business, Home Premium and Home Basic, when you try to add additional features via Control Panel > Programs and Features > Turn Windows features on or off, the process may take a very long time, and you may receive the following error message:
An error occurred. Not all of the features could have been changed.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB967256.