Administrator rights

On Windows XP this means Limited User Accounts can not run the game and on Vista and later these either require UAC to be disabled, there's a prompt to heighten their permissions to admin level, or they need to be separately run as administrator.

Likely caused by DRM or poor design on where the game needs to access data, though admin rights may be temporarily needed for automatic updates (if the need is limited to them, they do not belong here).