This morning, I was trying to clear memory on my phone so the battery would last longer. I went to Settings>Applications>Manage Applications, and I started going through the list and pushing the "Clear Cache" button. I pushed in on "Settings" and then the screen cleared and went back to my home screen, where the background was some random picture I've never seen before. It didn't recognize my memory card for me to change the picture, so I had to take it out and put it back in. Now, all of my notification sounds are this random song, and when I go to change the notification sound (for gmail or text messages), there are only the ones I have created in the options list; all of the original sounds that were on the phone before are completely gone! What did I do and how can I fix this??