The first thing to look at is the MD5 checksum of the ISO you just downloaded. The MD5 checksums are available right from Mandrakes web site:
http://www.mandrakelinux.com/en/ftp.php3
If the checksum is different from your downloaded ISO, you can use the DVD's for drink coasters, like I do.
Was the Fedora you burned a DVD or a CD-Rom? If you can boot from other DVD's in the same drive...