Are you referring to music in your library or searching for music videos from the Internet using RealPlayer?
If you are referring to your music files in your library, you can add them back to your library as long as you have the files in the hard disk. Here are instructions to scan files and add.
If you are referring to searching for music videos from the Internet using RealPlayer, please note that you will get better results if you use a Web Browser and go to websites such as YouTube etc. and then download the videos using the downloader.