You can P/Invoke SHAppBarMessage() to create a task bar. The APPBARDATA.hWnd you'll need could simply be the Handle of a Form class. Anything goes as far as what you display.
Getting the notifications you'll need to make the task bar display active windows is going to be a whole lot more difficult. You'll need to use the global WH_SHELL hook, set by SetWindowsHookEx() to receive the notifications you'll need. You cannot set this hook in C#, it requires an unmanaged DLL that you can inject into a process. You'll find crucial help in this project.
Getting the Windows taskbar to not do its normal job is going to be impossible unless you somehow find the undocumented information you'll need. Microsoft doesn't document this for a good reason, the taskbar is an important part of the way they innovate on the Windows look-and-feel. Quite visible in Win7. They don't want any code to take a dependency on this, they'd have a near-impossible job of keeping the next version of Windows compatible. I'd have to recommend you completely disable the Windows taskbar and replace it by your own.