I closed the Add or Remove Programs program while it was updating packages. I assumed it would just cancel the process. I decided to reboot just to be sure, but when I opened the shutdown menu, the options had disappeared and I just decided to turn it off at the powerpoint. I then turned it back on, and when it booted into the desktop the background had turn grey and the icon images had disappeared. The menu had lost its logo and the shortcuts on the Application Launch Panel had their icons turned into X's on a blank document. Programs run just the same, except for Epiphany which lost the icons on its buttons. I use a Raspberry Pi 3 model B.