Reboot and Reinstall OSx Lion with Snow Leopard currently installed on my Mac I have Snow Leopard installed and only have the original disk of Lion that came with the Mini Mac. The Mac won't boot and stalls during the reboot phase. Obviously I don't have a recovery partition with Snow Leopard.

My query is twofold. First can I just put the disk in the dvd drive and try rebooting from the disk. Second, will I lose data and apps? If so appreciate guidance on how.
To boot from the DVD:


  Press and hold the C key on your keyboard immediately upon hearing the startup chime. Your Mac should start up from the OS X installer CD/DVD media.
  (source)