I followed the installation instructions but when it came to set the global.inc permission back to 644, the installation page kept on not recognizing.

That domain is running on a Windows Server, does your hosting company have some kind of control Panel to change file permissions. You won't be able to do this via your FTP client.

I think, that this last stage is not really required - you could try editing "config.inc.php" and changing the "installed" variable to 1
Then remove the install directory and it should work. I know this question has been asked before - so search the forum for the previous answer, which should have more information.

Jason