Files can not be played :( (Traktor problem)

So i bought a toshiba satellite over the summer with the intention of using it at house parties/ frats and the like (i'm a college student). But the main problem I've had with it is that traktor refuses to read any of my songs. I transfered everything over from my mac to pc via crossover ethernet cable, so it all shows up in the proper file folders and in itunes, but traktor still wont play them. Any ideas as to why this is happening?

--The error reads:

File can not be played

FIle can not be played; may be missing, corrupt and unsupported.

How did you transfer them over?? Same directory as before?? Did you also transfer over the collection.nml file?? If you did then it's probably looking for the files in the wrong place. right click on the track collection tab and click check consistency. Will probably take a while to run if you have a lot of files, but at the end it will tell you if it cannot locate any of the tracks, and you can also specify where they are from this screen.

You need to install Quicktime to play M4As and MP4s