How to migrate a physical files into Drupal 7
If the site to be migrated has low double digit numbers of pages or has widely varying HTML and document structure among the pages the easiest solution is copy and pasting it by hand. This may be an opportunity to reorganize the site, add taxonomy terms and clear up other minor content issues.

For larger sites there are several options:

The Migrate module provides a framework and API for you to automate content migration. Using it will involve some coding and require a degree of familiarity with Drupal. 

The Feeds module is generally used for importing data like RSS feeds but can be used to import site data. For example, it will import a CSV file, converting lines to Drupal nodes. I envision a solution copying pages into a structured spreadsheet with fields for Title, Author, Body, etc. and exporting that to a CSV for import via the Feeds module. 

For completeness I'll mention the Import HTML module which only has Drupal 5 and 6 versions available. If you found this module suitable to import your content you could import into a barebones Drupal 6 installation and perform a site upgrade to Drupal 7.