cubbies08

When I turned my computer on today, it was acting very strange. All of my desktop icons were gone except the recycle bin. I can't access anything that was on the desktop. I got this error message: /Desktop refers to a location that is unavailable. it could be on a hard drive on this comp, or on a network.

When I tried to access iTunes through the start button, I got this message:
iTunes could not be opened. an unknown error occurred (-50).

How do I get my icons back and what can I do to prevent this in the future? Thank you in advance!