How do you register a BHO DLL in Windows, and where is it stored in the registry?

To register a BHO, you use the command `regsvr32 helloworld.dll /s` with administrator privileges. This writes the BHO's CLSID to the registry under `HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects\{GUID}` and `HKEY_CLASSES_ROOT\CLSID\{GUID}`. Unregistration is done with `regsvr32 helloworld.dll /s /u` or by deleting the registry keys. See the original article for the full development process: Implementing IE Browser Hijacking Using BHO.