|mmm not sure I follow your process...|
"formatting from the cmd prompt..." How are you accessing/getting the cmd prompt?
Typically the C: partition is where windows will be installed; and you cannot ask it format the partition in which it lives and presumably is producing the command prompt - as in effect you'll be asking it to commit suicide (by formatting the partition and thus removing the windows OS itself).
If you have managed (somehow) to reformat the C: partition then the boot.mgr and all startup files will have been erased, along with the actual system files etc..
If you are wishing to re-install Vista then simply boot up with the Vista DVD (or CD whichever it is) and follow the on-screen prompts? This presumes it is a proper full version Vista disk (OEM or Retail). If it's a recovery disk then much the same process.. However the make/model of the laptop is important here as each has its own way(s) of going about a recovery process (factory restore/reset routine).
So what make/model laptop?