If you were copying files from the internal drive to an external, you can simply reboot, stopping the copy, and your songs in your music folder should be intact. If you were actually moving the files, which doesn't sound likely considering the timeframe involved, then some songs might be in your Desktop, some in your Music folder.
The biggest problem with having so many files on the desktop is that the Mac tries to draw icons for each file and bogs down to a slow crawl. If the songs are still intact in your Music folder, do the following:
1. Reboot the computer in Single-User-Mode (hold down Command-s at startup).
2. At the command prompt, type fsck -yf (filesystem check, accept "yes" by default, force check). If it finds any errors, run it again until all errors are gone.
3. At the command prompt, type mount -uw / to mount the root volume with write permissions.
4. Type cd /Users/yourusername/Desktop
5. Type rm *.mp3 if you want to remove all files with an extension of MP3. If you only want to move them to a new directory, type mkdir temp, then mv *.mp3 ./temp/, which should move all the MP3 files from the desktop to a new folder called temp.
6. Once complete, type reboot.
Hope this helps!
Bryan
