Since you are saying that you can still play your music, the files seems to be there. Don't do too much command line stuff if you are not too familiar with it.

If you have wireless access, you can enable sshd and use winscp to login from your Windows PC to your N900.

You should then be able to download the files.

If you don't have it, then the best way would be to connect to a Linux desktop, like Ubuntu/OpenSuSE, etc and copy files.

While you at it, get rid of the Windows desktop for ever. Migrate/upgrade to Linux desktop.

Good luck.