Hi warrix,
Did you transfer to your PRS-650 using Reader Library or Windows Media Player? If you used WMP (you mention that it recognises the Reader), then I'd suggest trying again but just use the Reader Library software instead.
Open the Reader Library software and connect your PRS-650 to your computer. Down the left hand pane of Reader Library, click on 'Computer' and then in the main pane of the software you should be able to navigate to the location on your computer where you store your music files. Once you've located the files, select the ones you want and drag them over to the left hand pane where you should also see your Reader listed. Drop the files on the main Reader icon (don't drop on the Audio icon below the Reader (if you have the sub categories displayed) as the software automatically assigns files to the correct sub folder for you).
That should be it. One thing to be aware of though - is make sure that your music files are in a compatible format. As you are using Windows Media Player I'm guessing it could be quite likely that your files are WMA which I'm pretty sure won't work on the PRS-650 (you need MP3 or AAC files), but you should find confirmation of supported file formats if you look in the User Guide on your Reader.
Hope this helps.
