A few things:
- Molex is a power connector standard which was used on everythign from old GPUs to PATA HDDs
- Sata power connectors are long flat connectors that are used specifically for SATA HDDs, and is standard across all SATA drives
- A fan connector is just a 3 pin connector, and while it is used for a lot of different things it is not appropriate to use a 3pin fan connector on a HDD.
Give us a little more information about what you are trying to hook up and we will be able to point you in the right direction for power supplies or adapters.