How to feed my speaker to my microphone?

There is a simple solution for this, Windows has build in microphone devices that allows you to record what Windows is playing. This feature is however, tricky to activate it. To activate, press right click the sound icon inside your system tray, press Recording devices. A window will show all installed recording devices, then press right click at the device list and select "Show disabled devices".

If you're have up to date sound drivers, there will be a device called "Stereo mix", press right on it and click enable. Now you can select this device at the microphone selection of your favorite chat program.

For more information about this topic (in case updating the driver won't help you), see: http://www.howtogeek.com/howto/39532/how-to-enable-stereo-mix-in-windows-7-to-record-audio/

Virtual Audio Cable may be what you need. It does require you to boot without checking driver signatures though, if using Vista and up. You have to keep pressing the F8 key on startup to bring up this screen:

Virtual Audio cable is also not free, and I have yet to find an alternative. The trial is fine, but you do get a small blip every few seconds, notifying you that it is a trial.

On Gtalk, set your mic option to Virtual audio Cable.