After default installation of WordPress on Windows Server, the administrator is usually confronted by an error which happens after the user is uploading an image:
This is caused by insufficient rights of the file.
Reason for this behavior is some PHP process, where the upload is first stored in c:\Windows\Temp and afterwards the file is moved to the target ‚wp-content‘ folder. By movement, the file privileges are not updated.
To fix the issue, the upload folder needs to be changed to a folder, where IIS_IUSRS has read and write-access to the contained files.
This can be done by change the PHP.ini variable (http://php.net/manual/de/ini.core.php#ini.upload-tmp-dir) and setting the file privileges:
; Temporary directory for HTTP uploaded files (will use system default if not ; specified). ; http://php.net/upload-tmp-dir upload_tmp_dir = C:\inetpub\temp\PHP