You can use any sound card: integrated, add-on card or external device (USB or FireWire).
Sound Card should have DirectX-compatible audio drivers.
Recording capabilities no longer depend on the "Stereo Mix" feature.
Yes, this is possible if some application already using the sound card in Exclusive mode.
Possible solutions:
Went into the soundcard controls and turn off 'Encoder'
Go to Control Panel -> Hardware and Sound - > Sound.
Right-click on Speakers, select the "Advanced" tab, clear the "Allow applications to take exclusive control of this device" checkbox
Yes, this is possible if you are recording from the "Speakers" in loopback mode.
i-Sound gets the audio stream "as is" without any modifications. The recording level in this mode depends only on the playback volume.
In most cases it's a problem with the secondary display. The recorder remembers the last window position and will appear outside the desktop if the secondary display is inactive.