Well i m having Cannon powershot A630 digital camera. Can i use it as web cam? If yes then how?

Please do not suggest me to buy a web cam instead!

no never

It's possible if it has Video Out, AC/DC and your system has AV In and your chat program supports it.

No.

i guess u cant do it, but still if u have a tv tuner card try plugginging in ur cam output to the AV in but i donty think it will work