Ok I too have run into the multiple user problem on windows XP. MC9 will only run if the user is Admin.
But I have a workround. Here goes...
1.Create a new user called MCUser and set a password
2.Make this user an administrator
(log on at least once before next steps)3.Create a new shorcut (Right click desktop/new/shortcut)
4.In the location box type the following;
runas /noprofile /user:yourmachinename\MCuser "D:\Program Files\J River\Media Jukebox\Media Jukebox.exe"
5.Click 'Next' Give it a name i.e.MC9 and click 'Finish'
6.Right click the new icon on your desktop click properties and select 'change icon' on the shortcut tab. Browse to D:\Program Files\J River\Media Jukebox\Media Jukebox.exe and choose one of the loverly MC icons.
6. Cut the icon and paste it into the desktop folder for your other users (or the All Users desktop folder).
7. When the user with the'Limited' Account clicks on the new icon they will be prompted for the password of the MCUser account.(see below)
Heypresto MC will run!!
Why ? Because the shortcut runs MC under the MCUser account which has admin rights.