Editing the source of signature files?

When creating signatures I have no problem inserting the picture, however, if i want to link that picture I get a goofy looking hyperlink box around it. I want to be able to edit the source of my signature to include the border=0 tag. Copying and pasting doesnt work and I really hate having to link to images on the web rather than just attaching them to the message. How can I edit the source of an existing signature file and where is it stored?

unfortunately you can’t edit source and set border to 0. I will add this to our feature requests list and in future we will try to implement some possibility of editing this border.

Sorry but it seems to me that I paid 50 bucks for an awful lot of restrictions on the hope that some day the features I need will be implemented.