You can't format your hard drive without loosing anything that's in it. How severe is your laptop issue? After the power interruption, where there any errors showing on your screen? If there's no error, there's no need to format the whole drive. Just start your download of the program and all should be ok.
You could perform the chkdsk /r command on your hard drive via the Command prompt.
Make sure you have a backup of your system before performing any operations.
Hope I helped.