Ok, so I'm think about reformatting because my PC has been running terribly slow. But, first I got a message early when I was turning my Computer on that said System Fan is out and something else. Would reformatting fix that? And Also how exactly do I reformat?
No reformatting would not fix that. What that message means is a piece of hardware(The fan and something else) is bad. To fix this depending on how good you are with fixing things, either take it to be repaired or locate the bad fan and replace it.
First of all.... just because your PC is slow doesn't mean you have to reformat it, there are other ways to make the computer faster.
Also, reformatting would not fix the fan issue as said by Firestar. It sounds like either the fan is not plugged into the motherboard, or the fan has died. If the fan has died, replace it. But before doing so, make sure it is plugged into the motherboard first.
Good Luck!
Also, make sure the power cable is unplugged from the computer before you work inside the case. Also, ground yourself [touch something metal, like the side of the case you took off to get into the case]; You know, basic stuff. =) I hope you're able to find a replacement fan, because most repair shops would way overcharge for simple work like that.