Files checked out by defunct computer

I have a user that has gone through (3) computers in the time they've been with the firm. While doing some maintenance of the server I noticed a bunch of files checked out to them. By looking at the "Checked Out In" column I could see that they were on different computers! Two of them are no longer in service. So those files are GONE.

What's the best way to handle this? 

SolidworksSolidworks Pdm/enterprise Pdm