I use "Save As ..." for many purposes as well. It's far easier, unless you want to repost to another thread after, say, the original thread is yanked. Those local copies of the images are as you say sitting on your HD. Your "saved" HTML has in fact been changed point to the local copies and not to the original sources on the web. The information of how to link the original sources has been lost, although you may be able to google it up again. Reposting will take some work.
Might as well mention that my 6.0.2 MSIE doesn't like old saved thread files with local pictures. In fact, it just doesn't like local pictures at all.