Evita - Activ uses the same Windows components that IE uses, even if your user has a different browser for surfing.
As far as building your pages goes, a lot of folks use Word to generate their web pages. Word creates web page code full of extraneous XML and proprietary markup, intended for users who want to re-import the web pages back into Word again.
If you use Word, you might want to visit this first link, which provides a 'clean html' option. I would also recommend running a cleanup utility on those pages. You'll have a much smaller set of files, and thus a smaller, faster ebook.
Here are two free utilities, one from MS itself: a Word Html filter:
http://www.microsoft.com/downloads/details.aspx?FamilyID=209ADBEE-3FBD-482C-83B0-96FB79B74DED&displaylang=EN
and TidyHTML, a nice cleanup and formatting utility:
http://tidy.sourceforge.net/
Both Dreamweaver and FrontPage accepts Word html, and can clean them up as well.
There are also several free html editors of varying quality; Arachnophilia, 1st Page, and HtmlKit are the first to come to mind.
As far as audio goes, html allows you to play some embedded sounds; you've no doubt encountered sites that start some sound or music upon opening. Search Google for 'html embedded sound' and you'll find a lot of examples.
Sunil also has a multimedia add-on, the 'Advanced Multimedia Extension', available at the 'EBookPower' link at the bottom of this page, to make the process of adding sounds easier.
best -
and I need to know the best, and easiest way to put it together. I don't have, or know, Word or Powerpoint.