Where would my originals be saved? If I delete them, can I still use the music from the iTunes media folder?

I have purchased a new laptop and followed the instructions to transfer my music from my old laptop to my new one,

by backing up the file to iTunes Media, copying to a removable hard drive etc.

Apparently now I have two copies of my music on my old laptop and want to delete one copy.

Which is better to delete - the iTunes Media file or where the songs were orginally (I don't know where that is)?