I've found several explanations online on how to do this. They are all the same. After downloading the revised acetmain.cui file:
Copy the unzipped acetmain.cui file to your AutoCAD support folder (making a backup copy of the original version) - e.g.: C:\Documents and Settings\YOURNAME\Application Data\Autodesk\AutoCAD 2009\R17.2\enu\Support (WinXP)
or
C:\Users\YOURNAME\AppData\Roaming\Autodesk\AutoCAD 2009\R17.2\enu\Support (Vista)
Run AutoCAD 2009 and start the CUI command
In the top left panel, switch to the current workspace, so that its contents is displayed in the right panel:
Click on the "Customize Workspace" button (turns blue)
In the left panel, expand the tree "Partial CUI files" > EXPRESS
Check the box by the "Ribbon Tabs" item
In the top right panel, click the "Done" button and end the CUI dialog with OK
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I've done this several times, tried resaving my workspace, restarted '09 and I still cannot get it to take. After I've checked the box for the express tools and click 'ok', it constantly reverts back to being unchecked.
What am I doing wrong?