Virtual sound card driver for Windows

I have no sound card on my machine, but I want to (automatically) record screen with audio on it. So I thing it's some kind of virtual sound card driver needed to loop back sound send to play to microphone. Is there such solution for Windows OS?

Not sure I 100% understand your question, but you might want to check out:

http://software.muzychenko.net/eng/vac.html

sounds like this might fit your requirements.

A cheaper virtual sound card with the same function. http://www.shiningmorning.com/VirtualAudioStreaming/index.html

Also includes a virtual webcam to broadcast/record screen/file. May consider the virtual audio+webcam package.

possibly of interest:

https://serverfault.com/questions/19601/virtual-sound-card-for-windows-server

or

http://www.datanab.com/audio/VAcard.htm

Virtual Audio Card

It's free and it works on Windows XP and it creates 3 Virtual Audio Cables as Windows Sound drivers.

It comes from a software kit for a commercial TCP/IP mp3 streaming device. Go figure. Works for me in place of VAC (Virtual Audio Cable) but the latency on my machine is pretty awful. YMMV

(from: http://club.myce.com/f57/creating-virtual-sound-card-win2k3-enterprise-server-170878/#post2530866)