How to convert slave hard drive to primary hard drive

current HD going bad, have second HD installed and using as back but now i need to make the second HD my primary, can i do this without having to reformat in order to add booting files? help

The easiest way to do it would be to back up your files and do a fresh install on the backup drive.

You could use something like partition magic to make a partition, and then install windows on that partiton.