Low level WinNT debugger

I don't think Ring 0 code will help. It did back in Win9x, and that's how TRW2000 works. However, I still cannot find any alternatives to SoftICE for WinNT. The problem I see is that the people at NuMega/Compuware seems to know something about WindowsNT that is not published. I can write a low level driver that loads. However, it is not low enough because it can still be debugged by SoftICE! What I want is something that is in the same level at SoftICE, so I can see and maybe alter the loading process of Windows programmatically.

I also suggest one good book.
"How debuggers Work",Wiley.
It tell you how the debugger works on windows and Unix .

Who is the author? And more importantly, do you have a soft copy?

And does it tell you about low level debuggers, or just the application level ones (ie the ones written using the Windows Debugging API)

"Good start point iz learnig how icedump or iceext work from his source code .. "

I am unaware where you can get icedump or iceext's source code....