Disk problems

I have recently downloaded phedora core 3 from the internet and attempted to install the system. I have a 2.6gh 512 ram 52x dvd cdrw computer, therefore I did not expect any problems. I ran a md5sum check on all the iso files and they checked out ok. I burned the disks at 4x and rebooted. I ran the media check on the first cd and it came out correct. I repeated the process for the other disks and none of the rest passed. Afterwards I attempted to copy disks 2, 3, and 4 to other disks of a different brand, but I got the same results. Finally I decided to try core 2, but unfortunately once again only the first disk worked. I have no idea why this would happen. By the way I also have win xp pro on my computer. Can anyone help me.