A. Did you have a previous version of XAMPP installed?
B, Did someone else originally set up Ubuntu on this machine?
If so 0
The version of the Linux distribution on your machine probably already has ProFTPd and MySQL installed. They may have also been configured to start themselves as services when the machine is booted. You need to disable them, then you can use XAMPP. You could also actually remove them, but that is not necessary. It is only required that Apache and MySQL do not automatically start.
Use these Google searches:
ubuntu 10 disable ProFTPd
ubuntu 10 disable MySQL