Windows 7 Beta Downloads

I downloaded the Windows 7 Beta in January, but only got around to trying to install it recently, I found that my ISO was corrupt, so I have a valid Beta Windows 7 key and no ISO. There seems to be no way of getting another copy to try again for free. So I am a disappointed user, with a disappointed 14 yr old son who was willing to let his mum nobble his PC!
Has anyone got a copy that I could try again with.
NB I have tried burning as slow as the burners will allow on 3 PC’s so far so I do think it is the ISO that is corrupt. 🙁