If you have a none working Microphone if you connect to a Windows 7 VM make sure the following things have been done in "advance":
1) Make sure the Windows 7 is a Enterprise or Ultimate Edition, other Editions of Windows 7 do not support this feature!
2) Make sure that the Registry Settings:
fDisableAudioCapture REG_DWORD 0x00000000
is configured in advance (restart the VM/Desktop if not!)
3) Make sure that Audio is configured in the RDP Setting @ the IGEL.
See also: http://support.microsoft.com/kb/2020918