^ Agreed. Do NOT try to do a true "Low-Level Format". In fact, you probably cannot get any tools to do this, despite the claims. Pointertoavoid is right, it probably is just a disk wiping tool. That is useful only if you really MUST destroy data on a disk.
If all you need to do is start with a "blank disk", the simplest way is to Delete all its Partitions, then start by Creating one or more new Partitions and Formatting them. These operations will NOT wipe out all the old data. But they will completely wipe out and replace all of the systems for tracking the use of sectors in files so that no file can be found again without fancy tools. If that's all you need, do the simple steps.
If you believe there are bad sectors on the HDD, your best starting point is disk utilities downloaded for free from your HDD manufacturer's website. They understand all the details of their drives and can handle them properly, both in terms of diagnosing problems, and in terms of finding and fixing minor errors.
At the time a HDD is manufactured and the REAL Low-Level Format is done, the controller board mounted on the HDD unit stores a bunch of information on which parts of the HDD it is using, which sectors if any are faulty and marked "Never Use", and which sectors are good but unnecessary for now, and hence are held in reserve as spares for automatic error fixing. As the disk is used, one of the background functions this board runs (even unknown to Windows) is to monitor all reads and writes for advanced indications of weak signals and bit errors. When it detects a poor sector it will copy the data from it to a known-good spare sector, mark the bad one as "never use again", and substitute the good spare in its place. If this all works, the data is preserved long before the sector is so bad the data are damaged. Windows will never know there was a "bad sector". As this work is done the HDD's board keeps track of it all and of the stock of good spares. One of the functions in the S.M.A.R.T. system is to warn you ahead of time if the stock of good spares is running low. If you get such a message, replace the drive soon while the automatic repair system is still working!
One function that the HDD maker's utilities can do is to force this internal error checking and sector replacement system to go through the entire disk and replace any questionable sectors it might have missed. It's a long process, but should be one of the first "fixes" you try if you suspect a problem, because it CAN actually recover data from a questionable sector before it fails completely and causes data loss. Note that this does not really fix a bad sector. It replaces it with a known-good one, preserving the data if possible, but Windows does not know this detail.
Also note that any software that really tried to do something like a Low-Level Format would severely interfere with this whole process, because it could fail to provide correct information to the HDD board's system, leaving it misinformed about which sectors are good, bad, and good reserves. SCARY!
If you run the disk maker's utility package and use all its diagnostics until the unit appears to have no problems, then is the time to let the OS start using it. As I said, if you're trying to re-use a disk and want to start empty, first step will be to Delete all its Partitions and then Create and Format one or more new Partitions. Then you can run Windows' Chkdsk utility to make sure Windows is happy that the whole disk (at least, the part that the HDD tells it about) is good. In fact, the easiest way to do that is to use the Full Format version during formatting. That will have Windows do its own checks on every sector available.