It's useful to know where 4D stores its serial numbers, in case you want to delete your licenses from a machine, or if you'd like to re-enter the licenses from scratch.

4D v6 on Macintosh stores both serial numbers and expansion pack licenses in:

System Folder:Preferences:ACI:4DV6Prf

4D v6.5 on Macintosh stores serial numbers and expansion pack licenses in separate files. The serial numbers are in:

System Folder:Preferences:ACI:ACI Serial

And the v6.5 expansion licenses on Macintosh are stored in:

System Folder:Preferences:ACI:ACI Expansion

4D versions 6 and higher do not use the invisible "xb" and "xx" files that were used before. 4D v6 and higher also do not tie any of the licensing files to disk sector information, so you no longer need to worry about losing your licenses after defragmenting your hard drive, or after restoring your system software to a drive that was reformatted, as was the case in previous versions.