I am also looking to do the same thing. I reformatted my computer and lost some music. The files are (fortunately) still on my Palm Pre, but I cannot find a way to copy those files back to my computer.
After I reauthorized my computer with iTunes, I WAS able to copy the songs I had purchased back to my computer. However, I have other songs that were imported from CDs and such that I need to copy back to my computer. Does anybody know a way to do this?
NOTE: USB mode does not show any music folders or files.