Try opening the files in Sound Recorder (it should be in Programs>accessories>entertainment).
Goto file>save as and look under format. If under 'name', there is anything other than "CD quality", change it to "CD Quality" (44,100Hz, 16 Bit, Stereo at 172Kb/Second) and re-save. This, I think, is what the error message is referring to.
Hope this helps!