I keep my personal stuff off my work machines specifically because I'll be handing them back intact. If you've done some work on that machine but not saved it anywhere else it's still company property and wiping the machine is destroying it. No one is likely to give you trouble over it unless they go looking for something you supposedly had, but if they wipe it instead of me there's no risk of a misunderstanding.

This is good practice anyway, if your laid off or fired unexpectedly, likely your going to be locked out of your machine without notice and without opportunity to clean up.