No Line-In/Microphone Levels or Unmute button

Hi - I plugged in my microphone in but cannot get sound to come out of the
speakers.

Vista has provided no 'Microphone' or 'Line-In' Levels in the
Sounds>Playback>Levels tab, or an 'Unmute' button.

When I was using Vista Home Premium 32 I found a registry fix that created
an 'Unmute' button in Sounds>Playback>Levels that could be un-checked to
allow the sound through, but now I'm using Vista Home Premium 64 the registry
folders are different.

The 32-Bit registry fix was:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\4D36E96C-
E325-11CE-BFC1-08002BE10318\0000\Settings\filter\SpeakerHp
and involved changing the binary value of a folder called
'EnableInputMonitor' from 0000 to 0000 01.

This worked fine, it didn't give me input levels, but it did create an
'Unmute' button for 'Input Monitor' that I un-checked and immidietly heard
sounds from my microphone coming through the speakers.

Now when I try to change that registry value I can't because if I try to
follow the same registry pathway
(HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\4D36E96C-
E325-11CE-BFC1-08002BE10318\0000\Settings\filter\SpeakerHp) there is no
folder called 'Settings' in the '0000' folder.

Please help, I am a computer idiot and desperatley require the aid of a
Mighty Brain.