Experimenting with the Flirc without the Flirc software and drivers installed, it appears that Flirc's native USB HID input to windows is limited.
The only reference I have is to use the microsoft MCE remote which starts out with a limited keypad to begin with.
What I was able to determine is that the number pad, cursor pad, <enter>, <clear> (backspace), and play/pause controls work, but none of the Media Center Edition specific controls appear to work.
I also noticed that the MCE remote in the controllers section does not contain all of the microsoft MCE buttons... notably, the PC Pwr button (which is actually <sleep>)
Once the software and drivers were installed, using the "windows keyboard" layout provided the windows commands that I needed such as <Win-D> (show desktop) and, surprisingly, <ctrl-alt-s> (which is the keystroke trigger for my shortcut to put the computer to <sleep>)
Hope that this information is useful.
Beverly Howard