My old case has only POWER SW, POWER LED and H.D.D LED wires on it. Do I have to buy new case with POWER RESET wire on it for my new motherboard? Thanks for your time
If you do not want/need the Reset button then no you do not have to buy a new case. Although I think the reset button is a good idea you do not have to use it as it will not harm anything if not used.
No, the reset switch is not required. It is extremely convenient though; you may wish to mod one on yourself using a momentary contact pushbutton switch.
The reset switch is really not necessary.
It is used rarely.
If you ever need to do a hard reset, just hold the pwr switch down for 4 seconds to turn off your pc.