boot problem?

hi, i just recently aquired an old pc. its got a P1 133MHz, 1.5GB hd, 32MB ram. i was just wanting to mess around with it and put a distro like puppy linux, or even linux from scratch on it, just a computer to mess around with really. but, for some reason when i try to boot from a cd, it hangs up at "Insert bootable media in the appropriate drive". ive tried like 8 old linux .iso's that i had laying around, and it hung up on all but one, Coyote Linux. i am puzzled, why it would allow only one .iso to boot but no others. ive checked all connections and jumpers etc... i dunno, any any ideas much be greatly appreciated, thanks.