Hinterholzer:
You get these errors when you are trying to install the booking component, right?
If you are not able to uninstall it with Joomla system then it will be probably not installed correctly. Question is, why it was not installed correctly?
How to unistall component manually (for Joomla 2.5.11):
Delete these folders/files:
1. administrator/components/com_booking
2. administrator/language/{lang-code}/{lang-code}.com_booking.ini
3. administrator/language/{lang-code}/{lang-code}.com_booking.common.ini
4. administrator/language/{lang-code}/{lang-code}.com_booking.menu.ini
5. administrator/language/{lang-code}/{lang-code}.com_booking.sys.ini
6. components/com_booking
7. modules/mod_booking_customer_info
8. modules/mod_booking_search
9. plugins/search/booking
10. plugins/user/booking
11. plugins/cciDEALPlatformCustomPayment
12. language/{lang-code}/{lang-code}.com_booking.ini
13. language/{lang-code}/{lang-code}.mod_booking_customer_info.ini
14. language/{lang-code}/{lang-code}.mod_booking_search.ini
Database:
We do not remove database tables for Booking, because we want to save older data.
But there are data about installed component which we have to remove:
1. DB Table #__extensions, you can find rows by name:
ARTIO Booking Customer Info - (type=module)
ARTIO Booking Search - (type=module)
cciDEAL Platfotm Payment Plugin for ARTIO Booking - (type=plugin)
Search - Booking - (type=plugin)
User_ARTIO_Booking - (type=plugin)
booking - (type=component)
These rows should be at the end of the table if the component was last thing you installed in Joomla
2. DB Table #__menu, you can find rows by combination of menutype and path
All rows should have menutype 'main' and path starts with 'artio-booking'.
But if you have not Booking in administration menu, it is possible that there will be no rows for Booking component.
This should be all for manual uninstallation.
Then check your rights in all those paths: administrator/components, administrator/language, components, language, modules, plugins (set write permission for group and set correct owner of those paths)
Then try to install Book it! 2 again.