Upgrade problem

I doubt this can be undone but I am going to ask, I had a "doh!" moment.

I have an HP machine. It had Windows Vista on it and I have a Windows 7 disk. I decided to put the Windows 7 on it. Well, I went ahead and formatted the hard drive. When I went to install Windows 7, I then noticed the Windows 7 disk I have is an upgrade from Vista. Is there any "un-format" tools or anything I can do at this point?