Many times you need to work with more than one jquery version, especially if you are working with drupal6. Most of the funky jquery plugins doesn't work with jqeury 1.4 and below. And you can't upgrade drupal jquery to some higher version using best practices. On the other hand using hacks (changing core files) can cause problems with Drupal bootstrap, core modules, etc.
Best way to combat this situation is to use jquery noConflict() function. Add following lines to page.tpl.php above 'php print $scripts'
var $jq = jQuery.noConflict();
Then replace the $ with $jq inside the jquery files where you want to use above jquery version or simply put the content of those jquery files inside the following tags
And that's it, in this way you can use more than one jquery version within a single drupal installation.