When you already have CRM 4.0 enterprise edition installed for one organisation and you add one more organisation to it and then try to install outlook client for this new organisation, then sometime you get
"You Organisation Name\MSCRMServices\2007\AD\CrmDiscoveryService.asmx not found" error.
To resolve this error, just create a new folder on the server with your new oeganisation name under "you CRM installation directory\Microsoft Dynamics CRM\CRMWeb" folder. and then copy the MSCRMServices folder under CRMWeb folder to this folder. So will have two MSCRMServices folders, one under CRMWeb folder and another under CRMWeb\you new organisationname.
Now try to install outlook client and you should be able to install this time without this error.