RealDownloader doesn't download anything without user inputs. Our guess is that your RealPlayer is looking at your photos and videos folder (hard disk) which automatically adds to RealPlayer library. You can manage what RealPlayer should see/not see.
1. Open RealPlayer
2. Click RealPlayer logo on the top left and click Preferences.
3. Under "Watch these folders", remove the folders you don't want RealPlayer to look at.
If your issue is different, please provide more information.