Macbook halts when startup – boot from Lion upgrade DVD?

[thun]

Hi!

My Macbook Pro halts during startup. It won’t get any further than the grey apple and the spinning wheel. Tried different solutions (safe mode, PRAM reset, and so on), but for no good. I’ve taken backup of everything I want to save, and thinking this is a great opportunity to make a clean reset for a fresh new start. Is it enough to buy (download) Lion upgrade from Apple Mac Store, burn this on a DVD and boot from this? Unfortunately I’ve lost the original OS DVD…

Or do somebody else have any other brilliant solutions?

Thanks!
Bjørnar