i have a bad sector on my hdd .. which software should i use to seal it off ..

Where are you getting this information from?

What is the make of the hard drive?

A bad sector is basically an unusable sector. What is your goal? To retrieve data from that sector? Do you know that there is data on that sector?

If the hard disk is truly damaged there is nothing you can do about it.
A chkdsk /r should mark and attempt to recover data from bad sectors.
start/run cmd then type: chkdsk /r

A portion of a disk that cannot be used because it is flawed. When you format a disk, the operating system identifies any bad sectors on the disk and marks them so they will not be used. If a sector that already contains data becomes damaged, you will need special software to recover the data.
It’s not unusual for a hard disk to leave the manufacturing process with a damaged sector; however, this does not affect the overall performance of the disk as the damaged space is considered unusable.

For the price you pay for software you could buy a new drive.

i got the msg from norton ghost ... there is no data in that sector .. all i want to do is seal it off

It basically is. It is unusable.