You may see 'Windows requires a Digitally Signed Driver' error message while installing HTTP Debugger on unpatched Windows 7 computers.
The reason for this is that the HTTP Debugger driver has been signed with SHA-2 Extended Validation (EV) Code Signing certificate that an unpatched Windows 7 is not aware of.
Normally, Windows receives updated root certificates automatically from Windows Update. But, if you have disabled Windows Update or, for some reason, you have not installed the Windows patch that includes this root certificate, the above error occurs.
Resolution - Install Microsoft Security Advisory 3033929 Update
Availability of SHA-2 Code Signing Support for Windows 7 and Windows Server 2008 R2