Hello,
I have not yet found a way to get a drop down menu to work reliably in the HouseMenu in IE7 (ie. to work like Solpart) so I just use static menus with the HouseMenu where the submenus are displayed along with the main menu items.
Eg. You can see this in action here: (This is for a vertical menu)
Free Skin - Simple Red Leaf CSS SkinFor a horizontal menu I have created a tutorial which demonstrates different methods for creating horizontal sub menus which is compatible with all browsers:
How to create Horizontal CSS menus in DotNetNuke using the HouseMenuHope this helps,