How can I remap the control keys on the keyboard?

[Typhoon <tanfeng@xxxxxxxxxxxxxxx>]

My mini notebook's keyboard shares the arrow keys(Up/Down/Left/Right) 
with browsing keys(PageUp/PageDown/Home/End), 
which is not convenient while surfing the Internet or reading an article.  
I found the keyboard has four control keys (Alt_R/Win_R/Context/Ctrl_R) 
which I rarely use, so why not make use of them?
After one hour of work, I have successfully remap the four control keys 
to browsing keys respectively on  the Windows XP by hacking the 
Registry, It works great.
But  I still have not tried out the way to remap on my Fedora Linux 
after two days, I added the following lines in the file
/etc/X11/Xmodmap:

 keycode 0x138 = Home
 keycode 0x15c = PageDown
 keycode 0x15d = PageUp
 keycode 0x11d = End

But the X does not care of these.

It seems the loadkeys also does not allow to override these keys.
Is there anyone know about it ? Any help is appreciate.