How to update jQuery to version 1.4? I installed the jQuery Update module, version 6.x-2.0-alpha1, which supports jQuery 1.3.2. I need to update it to jQuery 1.4 or higher, for a jQuery plugin.

I tried replacing the existing jquery.js and jquery-min.js files in the jquery_update/replace directory with the latest jQuery files, and made some changes to jquery_update.module as suggested in Using Newer Versions of jQuery. After doing so, jQuery started loading from misc/jquery.js, which was an older version.

Is there any simple way to update jQuery? I cannot implement the noConflict solution since I will be using third-party jQuery plugins.
The dev version of jQuery Update for Drupal 6 will get you up to jQuery version 1.7 (but it does break some of the admin UI).

There are a few patches available, (see Fix jQuery 1.7 for Drupal 6 and the Issue Queue in general), with varying reported levels of success.

If you choose to go down the 'manual' route then you'll have a lot of core/contrib javascript to fix. I think your best bet would be to base whatever solution you come up with on the current dev release of jQuery Update.

If you specifically only need version 1.4.2, then there's some instructions on how to do it here.