Cannot boot with 2 hard disks

I hav an AMD athlon xp 2500+ processor and a nvidia nforce 2 K7N2 Delta motherboard. I also use 2 hard disks. I had no problems. But recently the motherboard spoilt due to lightning. I change it to a nforce 2 ultra 400 K7N2 Delta2. but now i cannot boot up with the 2 hard disks. It sought of hangs during boot up. If i disconnect one hard disk it is able to boot properly.