File Permissions Must Be Set Correctly for Machine.config, applicationHost.config, and the root Web.config
File permissions for the Machine.config, applicationHost.config, and the root Web.config file must be set to read-write for a local administrator. Each file must also be a well-formed .xml file. If either of these conditions is not met, the setup program will not run, and an error message will be posted in the Platform Validation page.
To unblock setup, open the Properties folder for the file, click the Security tab, click Edit, add a local administrator, and set that administrator’s permissions to at least read and write.