If your application uses 32‑bit programs, your install process should copy the KeyChk.dll file to your Product’s program folder. Do NOT copy it to the Windows "System" or "System32" folder.
If your application uses 64‑bit programs, your install process should copy the KeyChk64.dll file to your Product’s program folder.
For more security, you may want to rename the KeyChk DLL file to something that will blend in with the names of the files that are included with your Product. This is allowed, but be sure to change the filename that is referenced by your Source Code.