"Bleeding" when trying to record on laptop

[Aud8k]

I'm trying to record some karaoke but every time I play back the recorded track, the music is "doubled" with a slight delay, as if the laptop's built-in microphone was picking up the music along with my voice. Here is an example:

http://www.singsnap.com/karaoke/watchandlisten/play/c58ef46c3

Notice how those staccato notes are doubled with that slight delay.

I'm using Windows 7 on a Dell laptop with Realtek.
Under Playback I have two devices: Loudspeaker (enabled) and Realtek Digital Output (disabled)
Under Recording I have: Microphone (enabled) and Stereomix (disabled)

I'm recording using headphones and the laptop's built-in microphone. This is what the Realtek Audio Manager looks like:



It's in German but most options are self-explanatory.

If you could help I'd be very grateful.

Thanks for reading.