How to identify where a particular block come from?
The easiest way for Drupal 6 would probably be to use the Contextual links module.


  Hover over nodes, blocks, and views blocks to expose styled
  edit/configure/delete tabs.


It's a backport of the same functionality that is in D7 core, but for Drupal 6.

Just hover over the block on the front page, and hit edit to edit that particular block.