Could not access network location %APPDATA%. You keep getting this error when you try to upgrade iTunes. You tried to uninstall and reinstall, but couldn't install again, then received same error message.
You can download and install an update for Windows Vista (KB936824) from Microsoft. It has fixed that error you are receiving. Try to install iTunes after you install that update.
1. Disable User Account Control (user account control control panel then select Never Notify), no need to restart despite what it says.
2. Use your Windows key + R to open a run dialog.
3. Type "cmd" and press enter.
4. Type setx appdata "C:UsersJRAppDataRoaming" including the quotes and press enter.
5. Log out or restart your computer.
6. Try opening itunes or reinstalling it.
Yes you can set it to off and see if iTunes install will work. If not, a removing and reinstalling iTunes, QuickTime, and other software components for Windows Vista article from Apple support has instructions to properly remove iTunes. Please remove Apple software in order as suggested.
Sometimes components used with iTunes cause problems and they must be removed completely. Another tip is to remove following folders even if they aren't deleted after uninstalling.
You might want to run CCleaner in Windows safe mode with networking. Basically, CCleaner will remove any files, folders, and registry entries from iTunes that it's uninstaller doesn't remove. Reboot your computer and then download and install iTunes if you don't have latest version 9.2 on your computer.