To do that with all your WB skins, you'll have to create new graphics for the right side of the Startmenu, and adjust the content, and sizing margins accordingly. Open Artemis, and Artemis Standard in SkinStudio and you can see the difference. Hopefully someone will come along and explain this better than I can.

btw........ your screenshot didn't really need to included anything other than the two Startmenus, did it? 

If I'm not mistaken, the "compact" start menu feature is restricted to WB4 and Winxp. You can change it yourself in skin studio, (if you have it) by making the width of the places list (right side) smaller. You may have to adjust some graphics to do this. However.to do this on every skin you download would be tedious work. This feature is is done (or not done) by the author of the skin. It is not a feature that you can select that will affect all your skins.
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