I was trying to install PowerPivot for SharePoint the other day in an existing SharePoint farm and it kept failing with the following error:
“cannot load file or assembly ‘Microsoft.AnalysisServices.SharePoint.Intergration, Version = 10.0.0.0, Culture=neutral. PublicKeyToken= 89845dcd8080cc91’ or one of its dependencies. The system cannot find the file specified.”
It turns out that the Installation Configuration .ini file stores a port number for the Farms SharePoint Central Admin site. Not sure how it comes up with the port number, but modifying the entry in the .ini to correspond to your existing Central Admin site, prior to completing the istall to seems to solve the issue.
The ini file is found at C:\Program Files\Microsoft SQL Server\100\Setup Bootstrap\Log\YYYYMMDD_1234567\ConfigurationFile.ini