The security folder is not in the htdocs folder but in the C:\xampp folder, if that is where you installed XAMPP, for security reasons.
If you re-installed into an existing xampp folder before stopping all XAMPP components and uninstalling any XAMPP services including the XCP before deleting the xampp older, then you may have created many issues that may only be resolved by once more uninstalling and making sure the above is observed.
After uninstalling the services, reboot before trying to install again and make sure that no XAMPP components or services are still running using the Task Manager and the Services Manager before attempting to re-install XAMPP.
Don't elect to install services when using the installer version, these can be installed after a successful and tested install.
Also try an alternative install version like the EXE(7zip) or the zip version and extract to the root of a drive like C:\ for example and then simply run the setup_xampp.bat file to set all the paths.
Then test your installation by running all the demos from http://localhost