Use RevoUninstaller to remove Bandizip. Make sure you use the Advanced option to remove all leftover files/folders registry entries
Install and run RevoUninstaller (freeware version)
Options tab (along the top) > Uninstaller (LH column)
Untick Make a Restore Point before uninstall
Tick Checkmark all leftovers by default
Uninstaller tab > Double click the desired program
Run the uninstallation process
IMPORTANT DO NOT reboot even if prompted when completed (Cancel if prompted)
Select the Advanced button and then run the process to remove all leftover files/folders/registry entries left behind after a normal default uninstall process
If prompted at any stage previously, now do the reboot
Check the file association. If Bandizip has gone, just re-install it (it shouldn't re-associate itself)