Acquiring another copy of Vista if I already have a CD-key?

[DainBramageStud]

Hi, I have a Toshiba laptop, and I need to reformat. This presents a problem because when I bought it it didn't come with an OS-CD. I do however have a valid CD-key printed on the back of the laptop which worked when I installed it the first time. I don't have a Vista CD handy, nor do I know anyone who'll lend me one. My question is this: can I download an ISO from Microsoft's website and use the key on that (I've searched the site and can't seem to find an option), [b]OR[/b] download a torrent and use the key on that. Would downloading the torrent be illegal seeing as I do actually own a valid key, and would only be using the key on that particular copy? Or is it illegal anyway (probably is :smith:)

If neither of those options work I guess I'll just have to rely on Linux and WINE. :v: