If (using Inno Setup) I install MyApp to C:\Users\User1\MyApp and create a shortcut on the public desktop. This shortcut correctly points to C:\Users\User1\MyApp\MyApp.exe on the desktop of User1, but it points to C:\Users\User2\MyApp\MyApp.exe on the desktop of User2!
I understand that creating a machine install in a User folder is asking for problems, but we are stuck with many customers who have exactly done that in the past (when we had a more or less per user installation). So how can I make the shortcut point to the Users\User1 folder for all users?
See my lengthy replies in the news groups.
In summary, User2 can not reliably access User1's profile, and it seems that Explorer is changing the target to suit. It may only do this if 1) it can't access the folder or 2) it's on a domain and assuming roaming profiles, but as it's undefined behaviour, it could do anything.
Your best bet is to stop it from installing into under c:\users (or the O/S equivalant).
If you have users will be upgrading from a "per user" install, you will need to use a different AppID so it doesn't attampt to upgrade the existing installation.