the disks are independent from the keys. So if you are being truthful, you can someone else's disk and just type in your key when it asks for that step.
Or on microsoft's site, you can get in touch with them to order another copy of the disks (i don't know how much they charge).
http://support.microsoft.com/kb/326246
I wouldn't recommend downloading potentially illegal disk images from the internet, you do not know if they are genuine or have viruses.