Problem with drag and drop

Okay, so today I got my sansa c150, and I link it up to my computer, so I try to drag files on and it’s takes forever and says that I can’t put the music in. After a while I try again, but for some strange reason it lost the data folder. So I try to drag and drop, yet it still doesn’t work. Can anyone help?

i’ve got the same problem, spent most of the morning trying to transfer 4 songs from my computer’s hard drive & it’s giving me the same error messages.