How can one use his digital camera as web cam?

Depends on the digital camera, make and model, and if it has been made to allow you to do it.

you can't do it with all cameras. please provide more info about the camera.

should be in the manual...
if it can then its either a manu you go to and put it into webcam mode or a button you press. most digital cameras can. then you plug it in, start yahoo, msn etc and its usually picked up. thats the general way. might not always work

Not all digital cameras work as webcams. Some do, and some don't. Best way to find out is to have it plugged in and turned on and see if yahoo messenger allows you to use/picks it up as a webcam.

Not all digital camera's support web images live transfer!

I recommend a A4Tech web camera. It's really cool and have good quality and has a microphone build in system.

Bye

get one with a usb connector. plugged it in and see if the windows detect it as plug-and-play. Once it seems like windows accepted it then launch yahoo messenger then start using it as a webcam. Some of the cheaper models will let you use it as a webcam at the same time as a digital camera.