I've got a collection of AKAI CDs that I've got as a birthday present and I don't have a AKAI hardware

I tried to use Kontakt to convert the AKAI cds into wav files, just using the AKA Batch Converter, but I get some funky wav files. Those files are with wav extention, the filesize indicates that the fles do hold some information in them, but I can't open those files in any of the sound editing software of any multimedia player on my windows xp.

Windows Media Player reported an error saying that it can not play the file, because the codec is missing. I didn't know that there was a wav codec out there that would not be preinstalled with Windows operating system.

Does anyone have any idea what's wrong? How come I et the wav files that I can't use after conversion?