Patch files are available for updating Drupal which makes it much easier than the old method of unarchiving .tgz files.
Make sure to test this on a clone of your Drupal core files and your database.
Login to the Drupal install being upgraded as an admin. This is important because you will need to verify the update after you apply the patch.
CD to the webroot on hbfweb17 and create an archive of the core Drupal files:
gtar czvf drupal-5.3.core.tgz includes index.php misc modules profiles scripts sites themes update.php xmlrpc.php
Download a patch file and test it:
patch -p1 --dry-run < drupal5.3-to-drupal5.23
Apply the patch:
patch -p1 < drupal5.3-to-drupal5.23
In a web browser, load the update.php script and execute the DB upgrade script if requiured.