Browse to the following folder (this can be done by copying the below path into a Start > Run window or the Start menu search bar): Windows Vista, 7: C:\ProgramData\VMware\VMware Server\hostd
Windows XP: %ALLUSERSPROFILE%\Application Data\VMware\VMware Server\hostd\ Windows Server 2008: %SYSTEMROOT%\AppData\VMware\VMware Server\hostd\
Replace the file datastores.xml with datastores.xml.default. If the file does not exist, remove datastores.xml and restart the VMware Host Agent service. The file should be regenerated automatically.
If the problem persists, uninstall and reinstall VMware Server