Try this link:
Couple files to modify and you should be good to go. I'll paste a bit of the info here for the sake of future tek-tips searchers ;-)
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In Redhat
In your home directory create (or edited if it exists..) a file called .Xmodmap
In the file write entries for each keycode in this form:
keycode 115=F13
keycode 116=F14
keycode 117=F15
<snip>
Just for reference, these mean:
keycode 115 = left windows key
keycode 116 = right windows key
keycode 117 = right menu key
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In Debian
In your home directory, create a file called .xmodmaprc.
In the file write entries for each keycode in this form:
keycode 115=F13
keycode 116=F14
keycode 117=F15
These are previously defined keycodes (these are from using the program called xev it allows you to position your mouse in a window and press keys, the output in your terminal will tell you what they keycode is for the key you just pressed)... use xev to find out the keycodes of your other hotkeys.
Just for reference, these mean:
keycode 115 = left windows key
keycode 116 = right windows key
keycode 117 = right menu key
Now you will need to load these into xmodmap (to view the keycodes already in xmodmap do xmodmap -pk) by simply typing: xmodmap .xmodmaprc
This will load them into xmodmap and keep them there until you close x, you will need to reload them each time you start x, to do this you can simply add a line to your .xsession file. My own .xsession file looks something like this:
xmodmap .xmodmaprc
exec enlightenment
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JBR