Apple Application Support was not found. ...

I use Windows XP Pro.

When prompted that an update for iTunes was available (I think to 9), I went through the steps to do that. I also chose to update Quick Time; I did not chose to install Safari.
After the installation was complete (I just let it run, I did not sit at my computer and watch it), iTunes was not on my screen, only a box to reboot; I rebooted.
When I signed on, and tried to open iTunes I got the message "Apple Application Support was not found. Apple Application Support is required to run iTunes. Please uninstall iTunes, then install iTunes again. Error 2"

The iTunes stuff is my kids accounts; I do not have an account of my own. Each kid has an account that they access through their own login account on our home computer. I do not want to loose their Libraries.
If I "uninstall iTunes, then install iTunes again" won't that wipe out their Libraries? I do not want to do that unless absolutely necessary.
BUT.......when I look in the Program Directory, I do not see a Library file now. Has the file already been destroyed by the "supposed" upgrade; some upgrade!!!

I Googled the error and got information on the Apple Discussion Board that I should do the following:
1. Download and install WinRAR.
2. Right-click the iTunesSetup.exe icon and choose "Open with WinRAR".
3. Once the EXE is opened in WinRAR, double-click AppleApplicationSupport.msi and when the installer window is open choose "Repair".
4. Done! You can now run iTunes normally
I did that; problem is, there is NO "iTunesSetup.exe" file on my hard drive, so I can't even try that.

After logging in with my own Apple ID, I tied to find the thread that had this info, but could not find it.

Can anyone help my kids???

Thanks

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