My Mac Mini doesn't wants CD
Your DVD drive is probably done.
It's usual so what you can do is


use external DVD drive or
find a friend with a Mac and restore you DVD to 8GB+ flash drive (partitioned as GUID) through Disk Utility or
buy the latest Mac OS X (check if your Mini support it though) and restore it to USB flash drive.
You can also install Mac OS X on your HDD while put it in external box and using another mac.


Use option key to boot from flash drive.