Help with San Andreas car mods?

Hey so me and my brother have just started modding San Andreas for the PC and i downloaded a few cars for my game (Mustang, drift cars etc.) and my mods work fine.. And so did my brothers until about two days ago. We dont know what happened. He downloaded a drift car pack and track and he started up his game the other morning and spawned his modded car and for some reason it was just the regular car. None of his modded cars are working anymore hes reinstalled it 5 times and none of his cars are working now theyre just regular in game cars. Any ideas on how I could help him out?