You’ve got backups, right? If your hard disk fails, you won’t lose anything important. But I bet you know someone who hasn’t.
Don’t leave them on their own. Go out tomorrow, and get them an external disk, teach them to use it, and make sure that they keep on using it. Then you won’t feel as guilty as I do now.
Update: To clarify, it wasn’t my hard disk—it was a friend’s, and I feel guilty for not having forced a backup solution on them before it was too late. I’d thought about it, but hadn’t acted.