You are trying to install bitnami drupal stack and xampp. Both installers include an apache server that wants to take the 80 port. You can install the bitnami drupal stack on a different port. For example, the 81. You probably will get a similar error with the port 3306 (the one used by the mysql database). In that case, you can use the port 3307 for the bitnami drupal stack. With this approach, you will have two independent installations.
If you want to have all-in-one you can install the bitnami drupal module on top of the xampp. Please see the following link:
I hope it helps,