Well I can not comment on how things are stored prior to 3.0 as remember we did not support storing html in the database back then. In fact our whole typecast function was not in existence yet with older versions
It should be stored as something like this to work proper
<iframe src="" name="frame1" scrolling="no" frameborder="no" align="left" height="400px" width="450px">
<iframe src="" name="frame2" scrolling="no" frameborder="no" align="left" height="400px" width="450px">
Now on showproduct.php the only edit I would make is what I have outlined above in my last post.
Othwewise using 3.1 I am able to post show and edit html descriptions should I choose to allow html.
This line in editproduct.php shows we
convert the html to editable html here
$pdesc = un_htmlspecialchars($pdesc);
Make sure to redownload the build and make sure you upload all templates and php files