Carles P.V's Custom Scrollbar Control - Updated

This is Carles P.V's great scrollbar control that I have updated to allow the "themed" property to correctly draw a themed scrollbar under Windows Vista. Also tidied up the code a lot. Don't vote for this, as this is not my code and credit goes to Carles P.V (the Steve McMahon of pscode.com, lol). Comments would be nice tho.