Re: Clear out computer
As it is staying in the family, the more draconian methods of data destruction shouldn't be necessary. If your son has the only user account, it will be an "Administrator" account; use that to create a new "Administrator" account for his daughter and then log in with the daughter's account to delete your son's account, including all of his documents & settings etc. Doing this will retain the programs which have been installed.
If this doesn't go far enough, use the Laptop's system recovery method to reinstall the operating system, although this will mean reinstalling all programs as well.
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