computer wont restart

i purchased 2 a7m asus motherboards &got them both up & running, then changed the grafics card a couple of times on this one, now it will boot, but if u use the restart option in the shutdown menu it just wont boot. reset sometimes works.but not always. win98se,1200mhz. DDR ,all in wonder DDR 32meg new build , could the bios be corrupt??????????