Logitech Comfort Keyboard K290 function keys work as Windows 8 and multimedia keys by default. In order to get the normal function key behavior you need to hold the Fn key.

You can configure this using Logitech SetPoint software. This tool is for those who don't want to use SetPoint.

This application is mostly a Windows port of k290-fnkeyctl written by Marcus Ilgner. He's figured out what SetPoint does and how it can be done on Linux.

This tool depends on two components:

• libusb-win32 needs to be installed. I opted to install libusb-win32-devel-filter from here. Then I used install-filter-win.exe to add libusb-win32 driver to my K290 keyboard. It showed up on that tool's list with vid:046d, pid:c31f and mi:00. This is a one time setup.
• LibUsbDotNet is included and used as an abstraction layer over libusb-win32.

Run LogitechK290FnKeySwap.exe to swap the Fn key or LogitechK290FnKeySwap.exe /reset to put the Fn key to its default behavior.