Personally, I think it's not worth the trouble to use a HDD with bad sector. Your data might be gone anytime when the bad sector spread. And believe me, it will spread. There are no pre-emp notification on when it will spread. Worst is when the bad sector is at the beginning of the drive where the file allocation table is stored. Data in whole drive will be hard to salvage.
Hardware How to fix bad sector on harddisk, Maybe any shops can provide the service