This reply from Microsoft was precisely what I needed after asking about the efficacy of re-formatting.
1) No, the full reinstall does not remove "mbr" on which there might be a boot virus.
2) Yes,There are some 3rd party programs that can extract information from a formatted drive.
3) Yes, there are some third party programs that can remove boot viruses like solo antivirus.
4) Yes, it is not always important necessary to do a data security scan but in some cases it is important.
Please do not hesitate to let us know about the results of these steps, we
will be more than happy to takeover and work on the second action plan.
I would like to take this opportunity to thank you once again for choosing Microsoft.