Windows key for shortcuts

[nyuwa]

Sorry to bother you again, but

I would like to assign a number of keyboard shortcuts to the "Win
key", which is otherwise idle under Ubuntu.
I have Ubuntu 10.04 installed on an old note book PC (for
experimenting) and NO PROBLEMS to assign key combinations like "Win +
U" = Logout.

Under TuxTrans this does not seem to work. When I press the Windows
key in an attempt at assigning some shortcut, I get "ISO First Group"
and that's is - no combination possible.

Ubuntu help documentation -> http://Lin-transfer/MappingWindowsKey.htm

"First, we will need to edit or create the .xstartup file. This file
is run when the GUI is started, and will give persistence to this
modification. If the file exists, open your favorite text editor then
edit to include the following commands. If the file does not exist,
add the following to a new file and save it to "/home/user/.xstartup".

# Make the Windows key a useable mod key:
xmodmap -e "remove mod4 = F13"
xmodmap -e "keycode 115 = Super_L"
xmodmap -e "add mod4 = Super_L"

Note: You can type these three commands directly in a terminal window
to test them. If the first command returns commandline:1: bad remove
modifier keysym list (empty), then simply delete it or add a # before
it to comment it out."



There IS no such file and creating it was possible, but when I tried
to save it as instructed, I red a red-colored error, telling me I do
not have the required permissions. I am the only one using this
computer.

What am I supposed to do here?