Lost Pasword Window User Account

Dear all member !
Now i have one problem and i want u to help me.
my staff lost his password user account of window, so he can’t log on to his computer.
For my solving i want to format window again but he doesn’t want to lost his data. Do u have any comment from this point or have any software which can handle this problem.
Thanks in advance for helping this point.
I’m looking forward to hearing from u all.