AspDotNetStorefront appears to have installed properly and default.aspx loads, but any time you try to access a product or category, you receive a "404: Page cannot Be Displayed" error.
Solution
To resolve the issue in IIS5/6:
1 - View the site properties for the site in question in IIS
2 - Click the Home Directory tab, then click Configuration
3 - On the Mappings tab, highlight ".aspx" on the list
4 - Click Edit and uncheck the "Check that file exists" option