To unblock your unit, first check whether or not it has area blocking. That can be checked with the program DVDInfoPro (http://www.dvdinfopro.com/).  Run this program and see what it shows in "Region Control."  If it shows "RPC2" that means your unit has area blocking.  If it shows “RPC1” that means your unit is already unblocked. In the "User changes left" field of this program, you see how many area alterations you can still do.

Figure 1: Blocked LG GSA-4160B DVD recorder.

The process of unblocking the unit consists in updating your firmware with a version that is not blocked, a process similar to the compute BIOS upgrading.  To do that, you need to download an unblocked version of the your DVD unit firmware from the Internet.  Obviously you need to know the brand and the model of your unit.  At http://www.firmware.fr.st/ you will find the firmware of practically all DVD units and recorders in the market.  All you have to do is download a version identified as "RPC1" (in other words, unblocked) and run the program that you download.

After doing the firmware upgrade, you will have to restart your computer.  Check if the upgrade was successfully done running DVDInfoPro again and seeing if the area control code has changed from "RPC2" to "RPC1." Compare Figure 1 to Figure 2. Check the "Region Code" field: it is now "All".

Figure 2: Same DVD recorder, now unlocked.