"Do I need to buy another copy of windows?"
Basically yes if no-one will help you.
Dell, and other large players, buy Windows at very low price, but with restrictions on what you can do in the case of disasters like you've had.
This means that you buy their systems at a lower price, but to some extent you're mortgaging your future. It's just a pity that this is not made crystal clear when you buy such a system.