Immediately,  after i posted this question, i searched online and came up with camstudio. that was working fine for video.. but for audio, it was not. I think that was due to the problem in my microphone port. it detects no sound at all.  I will try all available and suggested softwares, then tell you the best one (from my point of view). 

rewire bro, thanks for your concern. I dont mind using the microphone, because that will be used to interact with my instructor. 

once again, thank you all my friends..