How to disable Amasty extension?
To disable any Amasty extension, please follow the next steps:
1. Edit app/etc/modules/Amasty_XXX.xml file (where XXX stands for the extension name/code).
2. Change "true" to "false".
3. Clear the cache.
Now the extension is completely disabled and does not affect any Magento functionality.
Please note, disabling module output under System >> Configuration >> Advanced does not deactivate the extension!