My approach for this is to tell the aspiring Linux user to buy another disk off Amazon. They're well under $100 and will arrive the next day.
I then carefully disconnect and remove his existing OS disk, replacing it with the newly purchased one, on which I do a clean install of Linux.
We can (or not) copy his files off the old drive, which then remains "on the shelf", in case he has a change of heart and decides Linux is not for him. This also provides him with the comforting knowledge (he can see it right there on the shelf) that his decision to try Linux is completely reversible. Very handy when converting a less-than-knowledgeable friend or family member from Windows to Linux (for reduced incidence of service calls)
I do this for myself as well, when upgrading every few years. Handy to have a complete backup drive, which was perhaps getting long in the tooth, and a fresh new, (often faster and larger) drive for the new install.
Biting the hand that feeds IT
