There is a trick to reinstalling IIS7x that is not well known. For those familiar with IIS 6.0, it is natural to try to uninstall IIS 7.0 (or 7.5), reboot, and expect it to reinstall fine. If it doesn’t, it is somewhat natural, thinking still in terms of IIS 6.0 here, to go try to delete the metabase.xml file (which for IIS 7.x translates mostly to the three config files stored at c:\windows\system32\inetsrv\config). Having deleted his config files, the IIS administrator attempts to install IIS, sees the installation seem to hang for an extended period of time, and then fail with a very vague error message such as:
“the server needs to be restarted to undo the changes.”
Unfortunately there is no hint given at this point to check the c:\windows\iis7.log file. If there were the relevant errors would be:
< WARNING! > Failed to detect if config redirection is enabled. result=0x80070490.Assuming config is not redirected and continuing.
< !!FAIL!! > LaunchCommand result=0x80070002
The WAS (Windows Activation Service or Windows Process Activation Service) needs to be uninstalled after IIS is uninstalled to properly remove the config files IIS uses for storing metadata and to properly remove IIS’ dependency on the old config files. Manually deleting the applicationHost.config file and redirection.config files after uninstalling IIS will produce this error.
Uninstall IIS (from server roles)
Uninstall Windows Process Activation Service (from server features)