M4A To windows media player format

a few months back i bought a CD about flash- it had this itunes thing on it and asked if i wanted to add all my tunes to the itune library. i thought "why not- that way ill have it in 2 formats".

did not think much about it until now ive got my new laptop and when you click on the file it wont play it because it is M4A.

Thing is- i could STILL play all these tracks on my old laptop through windows media player aswell-so maybe it was on BOTH formats? now ive transferred all music i can only see it in W4A format.

any suggestions?