You cannot post from your own hard drive.
You must first upload the image to a server.
Many ISPs give you a little "Home Page" of your own when you sign up for their service where they can host your images.
My ISP, Bellsouth.net provides 10 mb and has an easy "Photo Album" feature that allows me to upload my photos etc.
It's where I keep my train signature when I'm doing an "Ayn Rand" type of post.
<img src="http://prod.bsis.bellsouth.net/coDataImages/p/Groups/26/26091/folders/11507/55723eddiewillers.jpg" width="48" height="48">
Equals 