I have a small computer shop... all hdd are just cloned... now, I don't know how to format one of the cloned hdd... please help me with this because I think that some of the hdd has a bad sector already... and I want to reformat it and install the games manually on it... hope you could help me with this... tnx...

What exactly do you mean by cloned so we are on the same page before I can give an answer? Is this drive in raid config?

From question would think you could set the drive as slave and boot PC then use windows explorer to format the drive letter of the slave drive - with a drive with bad sectors, would choose to do a low-level format

Did not mention though if IDE or SATA drives

This is a pretty basic question that I am surprised a computer person would not know. Whether a drive is cloned or not has NO bearing on how to format it. A drive is formatted using the Format command. This means the drive needs to be hooked up to a computer and formatted.

I re-read and understand the question as written now, yes above is completely on mark.