>Windows7 now really looks nothing like Windows98 anymore
However, it remains consistent with the common controls. If you dropped W7 onto a W98 user they'd still recognize all the normal chrome (command buttons, listboxes, comboboxes, pop-up and dropdown menus, option buttons radio check buttons etc) and they would still all work exactly the way they expect them to work. Which is the whole point.
W7 (and Vista before it) merely added new metaphors, new controls and some new graphical tweaks (this latter mainly because they now have more screen space to play with since screen resolutions have gone up since the days of XP) to support those metaphors. It didn't change the old ones.
And as HughLerwill points out, you can use a manifest with your program to ensure it uses the Vista/W7 graphical tweaks (i.e your program will look like a native W7 program rather than an XP program)