Julie recently lost her job after 25 years, and now she has to return the laptop she used. She needs to wipe it first, though. Leo says that laptop is company property and everything on it belongs to them, even if she has personal things saved on it. There is no way they can prevent her from doing it, but Leo advises talking to an attorney before she does.
To wipe it, she should make a USB thumb drive with her OS on it, and then wipe it from the thumb drive. Windows 10 has a secure erase feature that will allow her to erase anything that she places in the trash can. It's probably the best idea to do that instead. She won't want to give her boss a reason to sue her after they just fired her. The program that Leo recommends is Eraser. Another option is Darik's Boot and Nuke (DBAN), which will wipe the drive and then overwrite it with 1s and 0s so the data can't be recovered. But Julie should understand that if she does that, they may not like it and may take legal action.
Hiren's Boot CD will let her make a bootable flash drive that uses Linux. In there, she can then wipe the hard drive. There's also the Ultimate Boot CD.
That's why Leo always says that she should sandbox her personal information by not using a company device to house them. Keep everything separate.