WordPress on Windows/IIS cannot upgrade, add plugins, upload themes
Feb 24
Windows Server 2008 IIS7, Windows Server, Wordpress 6 Comments
I have been struggling with this one ever since I moved my WordPress installation from my old Windows 2003 server to a new Windows Server 2008 machine. If I try to use “automatic upgrade” to upgrade to the latest WordPress release or upgrade or add a new plugin I get to the “Connection Information” page asking me to fill out ftp host name, user name and password. When I try to upload a new WordPress theme I get 500 Internal Server Error. I have understood that this is a permissions problem in the file system but have failed to be able to solve it.
I have been trying to give various users and groups permissions on the everything from the entire wordpress directory to the wp-content folder.
However what I did not realize until today is that (at least in my Windows installation) the group IIS_IUSRS does not have any group members but I should instead give the user IUSR permissions. Too easy… 
So simply do this: give user IUSR Modify and Write permissions to your WordPress directory.
Finally!
Feb 26, 2010 @ 11:02:07
Hi Friend
I was doing the same thing for days, adding the group, just added the user on the www directory in IIS as i only have the blog over there ;
thank you for your help.
M
Nov 12, 2010 @ 05:46:25
Thanks so much – I wish I’d read this a few hours ago!
IUSR is the key.
Nov 25, 2010 @ 05:32:02
Hi, thanks for the advice, I can now install plugins etc on my IIS7 Worpress installation. I have been struggling with this problem for hours until I came accross your blog. You saved me alot of time.
Mike
Feb 02, 2011 @ 15:06:19
Easy when you know how! Wish I had read this about two weeks ago
May 03, 2011 @ 09:29:31
If this doesn’t solve you issue you may take a look at this post. It’s a bug with the WinCache plugin.
http://codepolice.net/2011/05/03/issues-when-you-upgrade-wordpress-plugins-and-core-on-iss-7-5/