Windows 7: Files missing

Hi, this is my first thread and I would really appreciate your help. I have Windows 7.
I was installing i-tunes and when it asked to restart my computer I restarted it. When it logged back in the desktop was like in the beginning - the desktop theme was some default picture not the one I had put on, no additional programs were not installed and the worst part - my user folder on the desktop was completely empty! All of the folders My Music, My Pictures etc. had only Sample Pictures and Sample Music in them. I tried searching for my files but they cannot be found. Even worse - in My Computer the Local Disk is shown to be almost empty, like all of my files hadn't been there. So is there any way I can find and restore my files? Please, help!

You could try doing a System Restore to a point before you tried to install i-tunes:
What is System Restore?

• Open System Restore by clicking the Start button . In the search box, type System Restore, and then, in the list of results, click System Restore.* If you're prompted for an administrator password or confirmation, type the password or provide confirmation.

Tried restoring, but nothing changed for better. It seems like during the restarting process my computer has had a critical windows update. Any possibility that this is the reason for my missing files?

To reassure yourself, check the updates:
Windows Update - View Update History Details

You will see if all updates were successful. When did you actually try to install i-tunes?

It sounds like you have been logged in under another user account.
If you logout, what options are given?

Might have you enable administrator account? Close the all sessions and see how much are logged at logon screen.