Warning If you have Microsoft Exchange Server installed, do not remove the HKLM\System\CurrentControlSet\Services\msExchangeIS key. If you remove this key, it will remove your Exchange Information Store service and users will no longer be able to connect to the Exchange computer.
If Microsoft Exchange Server was ever installed and removed, or if you have had a failed SharePoint Portal Server installation attempt, remove the following if it is present:
Note This folder is the same as the %Programfiles%\Common Files\Microsoft Shared\Web Storage System folder listed in step two in the preceding section; however, if you attempt to reinstall SharePoint Portal Server after an installation failure without restarting the server, the %ProgramFiles%\Exchsrvr folder is placed in this location. If you do not remove this folder, the program may not operate correctly.