pc repair help

i no the 3 things to reinstall pc,s fdisk format c: and installing windows from floppy,s and switch bios to start from disks.but ihave a seagate 20gb.hard drive that won,t let me reinstall windows even after it worked before and i have half a operatig sys. on it now and i have a 15gb.HD.fireball one day out of the blue it froze,while playing black&white game so i ctrl alt del. but did,nt work so i push power button to turn it off,but all off sudden it went to save mode opt.,s not of them worked it just automaticly would restart so i reinstaalled AGAIN!!,