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The email contains a link that includes the URLs of all the gadgets from that tab. If you click on that link, you'll get a page that lets you add all the gadgets or only some of them to a new tab in your iGoogle page. Here's, for example, the link to my iGoogle tab about Google.
Google could generate a similar link for all your feeds and gadgets that could be used to backup your iGoogle page. After all, it's just a list of links.
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