Plesk server(IIS) PHP Settings:
I had some recent issues trying to install EE on to a Plesk server running php 5.2.5. Changing a simple setting within the Plesk admin area resolved the issue.
If you plan to use php 5.2.5 you have to run it as an ISAPI Extension instead of CGI. You can find this in “Site Settings” within the Plesk Admin.