Try out with this one:
I think the best way to delete the auto drafts is to log into phpMyAdmin and pull up the WordPress database you're using.
Then go to the posts table, sort on post_status, and all the auto-drafts will come to the top for ease of deletion.
and you need to make sure that you have windows authentication enabled in IIS, so it can actually log you in.
Just once checkout whether problem is in your blog blogPostUri
Hope this helps.