Problems loading itunes windows vista

Try click on start and put in %appdata% in the search bar and see if opens up your appdata folder properly. It might be pointing to an incorrect location in the registry if you can't access this folder.

If you are having problems with %appdata%, check the registry under
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders\AppData
It should say something like "C:\Users\_yourusername_\AppData\Roaming

Cheers.