I think the following should be easy and probably the right way to do this unless the separate custom table is being managed by some 3rd party system
a) Export existing table as a CSV file b) Create content type in Drupal with fields like you have in the table from which the data was exported c) Use node_import (http://drupal.org/project/node_import) module to import the CSV file exported in step (a) into Drupal as nodes into the content type created in step (b) d) Use views for listing out the data in the site and normal node add / edit / delete to manage existing / new data.
Cheers Anoop
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