Welcome to the forums!
Are the jumpers right?
Check the boot order in the bios.
System fan is the case fan. If it is connected with a molex, then the motherboard will not be able to detect it. You can turn off the warning in the bios.
ive managed to find that out through vigorous searching on the internet.
as for turning the warning off, there is no option in the bios to do so.
i am currently formatting my harddrive to see if that is the problem, but i really dont understand why its not finding it after the bios.