The 4 middle buttons jump you to different parts of WMC, from left to right - Recorded TV, TV Guide, Live TV, DVD menu (This one will come in handy below!).
The 4 Bottom buttons are for Teletext services but are pretty useless these days unless your provider of TV carries Text service signals that WMC is compatible with.
As for re programming the buttons on your remote (Power and volume should be programmable) I'm guessing that as it has the 'Green Button' it conforms to Microsoft's WMC Remote Standard - i Found this online - May be worth a try:
To program buttons on the remote control by using the learning feature
1 Place the remote control for Media Center PC head to head (2 to 3 inches apart) with the remote control from which it is learning.
2 On the remote control for Media Center PC, press and hold the DVD MENU and OK buttons at the same time until the remote control lights turn off (2 seconds). The remote is now in learning setup mode.
3 On the remote control for Media Center PC, press and release the TV, VOL +, or VOL – button, depending on which command you want it to learn. The remote control for Media Center PC lights blink once to confirm the selection.
4 On the remote control that is teaching the command, press and hold the button that you want the corresponding button on the remote control for Media Center PC to learn.
The remote control for Media Center PC lights blink twice to confirm the selection. If the remote did not learn the command, the lights blink quickly four times. To try again, repeat steps 1 through 4.
Hope this helps