Hi i have a g4 mac mini which has been working flawlessly until...

When switching it on, i hear the faimilar startup sound but it fails to load the OS just displaying a folder with a questionmark and then the apple faces logo.

I tried placing the OSX disk in the drive and holding down C to re-instal but nothing happens, ive tried the hardware test and am just presented with a blank screen with refresh and next buttons

Ive just no idea what to do im stumped, a visit to the appleshop?

Any ideas would be most welcome!