There really is no 'best' way. And it doesn't matter if these are mp3's or spreadsheets.
There are many ways to do it, and they are all 'good' as long as they work. Let me mention a view:
- restore from your regular backup (I assume you make a backup, because you don't want to lose your mp3's in case anything happens with the original version)
- copy to and from a USB-stick
- copy to and from removable hard disk
- install a home network (any number of PC's up from 2) and copy using Windows Explorer
- burn to CD or DVD, then read it on the other PC
- copy them to your home page on internet and download again
- copy them to or from a web folder(you might need to rent space somewhere)
- email (as attachment)
Pick your choice, depending on the circumstances.
Hope this helps.
What are the best ways to transfer mp3s from one computer to another? (both over the internet and when the computers are in the same room)