A direct upgrade from 1.4.x to 1.9.x might not be possible, but what I have found to produce good results for old database versions is an incremental upgrade to each new major version.
You can find the last release of each version : 1.5,1.6,1.7,1.8 on the Magento download page.
Test the upgrade on a dev server and start with version 1.5, extract the source code and configure it with your 1.4.2 database details.
Point your browser at the new 1.5 installation to start the normal Magento install process. Magento will then upgrade your database to the 1.5.x version. Remember to use the same encryption key from your 1.4.2 version. After each upgrade login to admin and log back out.
Delete the 1.5 source and then extract the 1.6 source and perform the same steps to upgrade the database from 1.5.x to 1.6.x. Repeat this process through each version 1.7, 1.8 until you are at the latest version (22.214.171.124).
Depending on your database size some of the upgrades steps may take much longer than others - up to 30 mins or more.
The Magento database upgrade is just one part of the upgrade process, you should take a note of all the modules installed in the 1.4.x shop and now reinstall these with the latest versions, this will then upgrade the module data in the database.
You will also probably need to install a new frontend theme or rebuild your existing theme using the new base/responsive themes.
I have found this process to work well in upgrading databases as old as v1.3.x.