My hardisk is full of viruses, need help to clean it!

Please help me! My Seagate 20GB hardisk was infected by viruses, and crash my hardisk. Anti-vir and AVG anti virus detected VBS/Redlof.e, heur/cryted/ spr/destart and wpcb.3207 virus. Anti-vir had clean the spr/destart and wpcb.3207 virus and I though had cleaned also the vbs/redlof.e, and heur/cryted virus. But when I scan my hardisk again, the virus is still there, i try deleting the folder.htt file manually which the vbs/redlof virus created but with no avail. What makes things worst is my hardisk seems to be unusable. I try repartioning and formatting my hardisk with Seagate's Disk Manager but still the virus, the old files and partition is still there. I performed a disk scan and it detected a bad sector in sector 170,171,9708,9709 and 11 other sectors. Can I still use my hardisk? Do I need to manually edit my hardisk to fix this problem? I really don't know how to edit my hardisk manually but if someone out there who can teach me how to manually edit my hardisk, I'm eager to learn. I really need your help guys! Thanks in advance! God bless!