Clean re-install of Mountain Lion - How to?

[Memphis]

Ok folkies, I'm hoping this will be a quick query even if it's just to confirm what I'm hoping isn't the case.

I've got ML on my MacBook Pro but it was an upgrade from Lion which in turn was an upgrade from Snow Leopard (I think it was that way around...). The performance isn't too hot so I want to clean re-install ML.

Now the query... Do I really have to fully redownload the ML installer to create a boot USB to do this? Or is there another way using the files already on the machine?

I'd really rather avoid the re-download but I guess it's my own fault for not creating the media in the first instance.

Thanks!

 

[Memphis]

Many thanks slinxy!

Will the recovery need to download the OS as part of the operation though? I have half attempted this once before and it sat all night re-downloading ML only for me to find in the morning that everything was still in place as if nothing had happened!

 

[Memphis]

Thanks!