Window Title vs Page Title
The title set with drupal_set_title() is both the page title, and the browser window title.
If you are looking for a module that can change tHE window title, you can look at Page Title.

If you want to be able to do it from A CUSTOM module, you can implement hook_preprocess_page(&amp;$variables) to modify the content of $variables['head_title'], which contains a modified version of the page title to use in the &lt;title&gt; tag.

function mymodule_preprocess_page(&amp;$variables) {
  $variables['head_title'] = t("The new HTML title.");
}