Mac Not Booting Apple Logo and Spinning Wheel

Hi Everyone,

I have a max with 10.4 installed which will not boot. Ive taken the disc out and checked using disk diagnostics on another mac and its okay. What I want to do is one of 2 things.

1. Fix the issue where I cannot login or

2. I have purchased 10.8 on usb and want to install a fresh OS on a blank hard disc and then boot my faulty mac.

Can I do any of these?

Any simple steps would be gratefully received

thanks