In the vanilla game, unlocking all crew members (Sal, Yumi, Neville) required tedious challenge series progression. The reloaded repack often included a registry tweak or a pre-modified NFSCarbon.exe that unlocked all crew cars and abilities from the start of the Career mode.
The original release from 2007/2008 (the actual Skidrow/Reloaded scene release) contained only game files and a crack. It was safe. Need For Speed Carbon Skidrow Reloaded