Buying a used laptop

Lately I have been considering purchasing a used laptop for a friend. And I am wondering if there are any potential security risks with purchasing a used laptop. I will for sure be doing a clean install of windows (even if they say it is a fresh install). But I wonder if I should be concerned about anything else, like on the hardware side of things. Are hardware keyloggers viable on laptops? I can not really think of anything else off the top of my head but would really like to make sure.

 

I would first check the laptop for any information left behind by the previous owner.
And reformat the computer after extracting the information to an external source.

 

If you're really paranoid you could flash the BIOS.