It might be the CD format created by your burning software.
Have you still got the ISOs on your hard drive? If so, try reburning them using strict ISO 9660 settings (I use Nero -
www.nero.com - discs readable in *nix and win).
If you haven't got them, you might be able to rip the bad cds using Isobuster (just google) and reburn the discs in nero or similar - which should save some downloading.
To check that the discs are faulty (not just explorer playing up), open the task manager, kill explorer and then restart it. My XP box sometimes hangs badly with CDs.
HTH
frogman