The easiest way to remove a Magento extension from your website is by uninstalling it using Magento Connect and your Magento Downloader. To do this, login to your Magento Downloader, find the extension and uninstall it. If this isn't working for you or the extension isn't listed in Magento Connect, here's how to manually remove a Magento extension.
Manually Remove a Magento Extension
Before actually removing the extension, it's important that we disable the Magento cache and if it's enabled, the Magento compiler. If we don't, we may get problems when we uninstall the extension.
With the cache and compiler disabled, find and delete the file that relates to the extension that you want to delete in the app/etc/modules directory. The correct file should be obvious based on it's name (eg. for Magento WordPress Integration, the file is Fishpig_Wordpress.xml). This is the file that tells Magento to load the extension. Without this file, Magento won't know that the extension is installed so none of the code for the extension will be run when Magento runs.
With this file deleted, the extension will be completely ignored by Magento. There will still be extension files in your Magento system, but these will have no effect on your website. If you wish, you can track down these files and delete them.
To complete the uninstsallation, refresh your cache before enabling it again. If you were using the compiler, rather than simply enabling it again, you will need to recompile.