The “could not access network location %APPDATA%\” problem is a message which is generally link to QuickTime, an element of iTunes installation. You can try and update the java which can be found in your control Panel. Just click the Java icon in order to update the application, or you may try to upload the “java” software from Sun Microsystems. After the download process, install the application. When the installation is finished, you may restart the system to be able to install.

I would guess that you are using Windows Vista, the %appdata% is a specific directory found in your computer.
For XP it is C:\Documents and Settings\yourusername\Application Data\
For Vista it is C:\Users\yourusername\AppData\Roaming\

You may also try to download and install the KB936824 update available for genuine Microsoft OS which can be found to this URL.

http://www.microsoft.com/downloads/d...f-b6aa22525dec