I cant delete any songs off of a MyMusix PD-6110...

Question

I bought 3 of these as a gift for my children. I had a friend down load the songs. On the first one she did 34 songs and 7 of them was some sort of .com commercial. I need to delete them; however there is not a way for this in the owners manual. How and what can I do? (Might I also add that there is not a phone number or website listed either...)