I came across this issue yesterday and wanted to let you know what I found and how you can go about fixing this.  The computer I saw this on was running Windows Vista but I imagine it could also happen on windows 7 or XP.  Anyways, I found that the laptop had a virus and this virus had hidden all the desktop, documents, and other files and folders to make it look like you had lost everything on your computer.  The first thing you need to do is make sure your anti virus program is up to date and run a full scan.  After that you should also go to http://malwarebytes.org/ and downloand and run a full scan of this also.  Once you know for sure you have gotten rid of the virus and or malware you can now download unhide.exe from http://download.bleepingcomputer.com/grinler/unhide.exe . Download this program and run it.  It may take sometime to run but once it’s done you should hopefully be able to see your files on the desktop and under the Documents folder.  **NOW GO BUY A BACKUP DRIVE AND BACKUP YOUR DATA!**.  You will have hopefully learned a lesson here and realize that you got lucky but next time it could be worse.  So please go buy a backup drive or use a service such as Mozy and backup your data today.

I hope this helps you as it can be a really scary to turn on your computer and think you have just lost everything. 

RG

I recently came across this problem and thought it would be an easy fix if I just reinstalled or repaired the itunes application, but I was wrong.  If you ever come across the message “Itunes cannot run because some of its required files are missing” here is what you need to do. 

1) Uninstall itunes and quicktime player. (don’t worry your music and videos will be fine as they are stored in a different folder than the itunes program and you will not lose your music.)

2) Uninstall quicktime player. Then restart your comptuer.

3) Now go to www.itunes.com and download the latest version of itunes and install this. It will install itunes and quicktime player. Once this is installed you will now be able to open up the itunes application and everything should be back to normal working condition.

I’m not sure why this error message comes up and wasn’t able to find out how or what causes this but doing a repair or reinstall will not fix this problem. Anyways, I hope this helps some of you and some of the fustration on this odd error.