Microsoft Group Policies, and other environmental conditions, can prevent MSI installers from installing when the user does not have Administrative rights. Follow the instructions below as a workaround for this problem:
1) If you have already tried installing the WorkGroupShare client as admin, log in as the administrator account and remove the WorkgroupShare client, as you can only have one WorkGroupShare client installed at a time to work properly.
2) Reboot the machine.
3) Log in as the user you wish to install the client for and run the attached installer. If the user has access to all of the files in the attachment, the installer will install correctly for that user.