Recognize page content in xml files

I have a site that was consist of .aspx and .xml files.

.xml files contains all the page content

.aspx files are the “wrapper” for the .xml files

Knowing that search engines crawl through page content, I can’t very well direct people to an .xml page because while it would display in the browser, it would obviously be viewed in its raw format (ugly and not navigational)

All URL’s are displayed as one or both of the following:

mydomain-com/afolder/default.aspx

mydomain-com/default.aspx

My links to not contain any other identifying id’s. What I’ve listed above…that’s it.

How do I get the search engines to crawl and display the content that resides in my .xml files in the appropriate manner?

Basically, how do get search engines to index page content that is located in an xml file, while still maintaining the look and feel of the website?