Reply to Transferring mp3 files into itunes

So I went through my old hard drive today and found a few hundred songs that I want to stick in a playlist in itunes. I selected them all, and pasted them into a folder on the desktop, then selected them all again and tried to paste into this new playlist in itunes... Every time I paste it, it transfers maybe 180 tracks, and that's it... I've gone through and manually played every song in this file on the desktop, all of them are working, but I can't seem to transfer all of them to this playlist!

Any ideas?