The world of 3D on Windows for business or scientific purposes has been in flux for many years. DirectX was intended for games and besides was for unmanaged code while Microsoft has been pushing for development to be managed code (and rumors circulate that the version of Windows after Vista won't even run unmanaged code natively). Then there was Managed DirectX (MDX), version 2.0 of which was suddenly abandoned just as it was about to get out of beta. Then Microsoft came out with XNA Game Development Studio at the end of 2007. This had three problems. First, it was for Visual Studio 2005 instead of Visual Studio 2008. OK, maybe we can live with that. Second, it was geared toward games, with the framework expecting the application to always and continuously compute the next frame. Well, I guess we can work around that. Third, it wasn't compatible with WinForms (or any other managed platform for desktops). It was on their list of features to add, but they ran behind schedule and nixed it. Big problem.
The correct and best way today to develop 3D applications for business and scientific domains on Windows is to use WPF (Windows Presentation Foundation), which is part of .NET 3.x. WPF exploits 3D acceleration hardware like DirectX and is fully accessible to C# desktop applications. And it's compatible with Visual Studio 2008 -- in fact WPF seems to be the primary reason Visual Studio 2008 was even built.
That's a screenshot of a WPF application I'm working on. The cylinder and metal cans were mathematically computed on the fly in C#, because they're such simple shapes. The hammer and chisel were designed in Blender 3D and exported to XAML. Using standard Windows mouse interaction code, the cylinder, cans, and hammer can be dragged around.