You cannot install the game with just part2.rar . You must download every part listed on the ApunKaGames download page.
Place all downloaded .rar parts into the same folder on your computer. download-need-for-speed-payback-apun-kagames-part2-rar
Once installed, launch the game using the NeedForSpeedPayback icon in the installation directory. You cannot install the game with just part2
Open the newly created folder, find the Setup.exe file, and follow the installation instructions. find the Setup.exe file