Formatting “Local Disk”(laptop)?
Your laptop comes with a recovery software. They are located in the default drive where windows is installed i.e. the C drive. These recovery files may take around 2 - 3 GB and differ with each manufacturer. Consult your manual and they should state how much space is taken by it. FYI, a 43GB HDD does not have an effective 43GB of available space.
Hidden partition is present in most of the computers, which is used for system restore. It is needed to re-install windows or restore your computer to the factory default condition. Your lost space may be there. A format alone would not remove that partition. You need to repartition your disk. If you format, all your data will be lost and you will need to reinstall windows. You will get all the windows default programs back but not anything that you installed yourself. If you do not know how to do it, you may encounter some problems so seek professional helpask someone who knows how to do it.