Among the activities I haven’t done on a computer in nigh on a decade now: Rebuilding the Desktop. (You don’t have do it on OS X.) I had to look up how.
You can rebuild the Desktop manually by holding down the Option and Command (Apple) keys while the computer starts up.[…] Click OK when you see the message “Are you sure you want to rebuild the Desktop file on the disk “your disk”? Comments in info windows will be lost.
Nowadays of course, we have the more-advanced “Repair Permissions” as placebo technique for whatever ails your Mac. ;)