For OEM Ready tests (and for Certified for Windows Vista) one of the requirements is to set up an interactive debugger. The documentation specifies Windbg since it allows you to do use extensions such as "!analyze –v" which will give you a ton of information. One question that then comes up is "How do get back my machine back to its original state before I ran WinDbg –I?"
Those are the registry keys in question that "WinDbg –I" changes:
When you set WinDbg –I, Windbg will add a new string value "Debugger" with a path to windbg.exe. There is also an Auto string value added.
The recommendation is to back up the registry key before running WinDbg –I. On one of my clean systems the key was existent but the Debugger and Auto values were missing. Removing those effectively rolled back my system to the state it was in before. But don't take my observation as official guidance.
On a final note, if you absolutely don't like WinDbg, you can use Visual Studio as your interactive debugger. Under Tools/Options/Debugging you will find a Just-In-Time section. If you click the "Native" checkbox, your application will break in to Visual Studio when a breakpoint is encountered.