Another approach, which works well is to get the computer name via the environment variable. The advantage of this approach (or disadvantage depending on your software) is that you can trick the program into running as a different machine easily.
Result := GetEnvironmentVariable('COMPUTERNAME');
The computer name environment variable is set by the system. To "override" the behavior, you can create a batch file that calls your program, setting the environment variable prior to the call (each command interpreter gets its own "copy" of the environment, and changes are local to that session or any children launched from that session).