Hi Brendan, in MoI version 4 you can see your license key in the Help > "About MoI" dialog.

You can also put in your e-mail address on this web page here and have it e-mailed to you :
https://moi3d.com/reinstall.htm

Also you can look in the MoI appdata folder, you can see the location of this folder under Options > "Edit .ini file" button. That will pop up a dialog box that will show where the MoI appdata folder is, your license key will be saved there as a text file named moi_vx_license.key .

- Michael