Actually, with the help of Mr Neil WindowBlinds the issue is resolved. Now the start menu is using a single texture across the whole start panel, cleverly transparent on the left, big enough to cater for expanded or tall start menus, and set to 'autocrop'. 
(Uvah - The problem was that the start panel is made up of five separate bits - top, left, right, bottom and 'more programs' - and trying to get a texture to match successfully across those parts is tricky, because this texture looks bad if it is stretched. Then in vista or Win7 you have to successfully get the textures to still match up when these sections are stretched or tiled to make the 'expanded' version of the start menu, or if the user has a taller start menu because it has a lot of programs pinned on it.)
Anyway, not really finished yet, but a lot closer.
And a new snapshot uploaded.
