All of your hardware could have been damaged by the overheating be it caused by poor case cooling/dust build up, a dodgy PSU or a combination of both.
I would recommend that anyone that ever purchases a computer with such a poor brand of PSU such as Bestec replace it asap, these types of PSU are used by most OEM computer providers in order to keep costs down, people using a computer for nothing more than school or office type work may not notice a problem but if you play games or watch videos ect the load on the PSU and other hardware increases and so does the heat.
Before replacing the present PSU I would suggest that you get it tested if only to satisfy for yourself that it needs to be replaced.
NB: Don`t forget;
the one thing that we do need you to check is to see if your case will accommodate a PSU that has an on/off switch, cheap brands like Bestec often do not and some older cases do not have an opening for the switch.