Changed Resolution On FO1>Now Computer>NO SIGNAL (+Needs CR2032 Batt.)

I was playing Fallout 1 and I was making sure the settings were optimal so the game performance will be at max & would run the best it possibly can. After I applied these settings and confirmed my setup the computer just displayed to the monitor NO SIGNAL. Everything seems to be in working order but I am unable to revive it. + -Xtra Info- The small screen on the CPU is telling me the battery voltage is low (CR2032 Battery) I do not know if this could be a part of the problem. Please help me out, this could be an easy fix but all I know is it’s not easy for me. Thank you for taking the time to view this Computer Wizards