So you have a complex issue. Power supply is suspect and probably the easiest thing to replace. Even if fans are spinning, it may not be providing the system with enough power to turn everything on.
If you really want to know for sure, you can buy a power supply tester for 10$ at a local PC shop. It will show you if the voltages are off. If they are it is also possible that the video card was damaged, but you won't know that until the offending part is replaced.