Certain users may receive the error message, "failed to expand shell folder constant "userdocs"" when installing eWallet.
First, make sure you are trying to install eWallet 6.1 or newer.
Next, if your user documents folder is mapped to a network drive and you log into Windows Vista as an administrator, you may need to implement the following fix as specified in this Microsoft KB article:
If that fix does not apply to your computer, or does not resolve the problem, you may have attempted to redirect your Documents folder to another location on your computer or to a network drive. If your Documents folder location gets corrupted, Windows no longer understands where your Documents folder really is. Open Windows Explorer and right-click on your Documents folder inside your user folder, then pick Properties, then Location, then click "Restore Default Location".