Missed your first post Neil. Sorry about that.
Tong is right on. Just find a 3rd party image hosting service (photobucket.com, flickr.com, etc..)
Get the URL for you image. Many of those hosting services will tell you the URL somewhere on the screen, but if you can't see the URL anywhere, right click on your image and click "properties" then copy the URL in Internet Explorer or just "copy image location" in firefox.
Then when writing your post simply click the button that looks like this:
and paste the URL in the resulting prompt and click OK.