Hi friends
Finally I am done with my requirement.I used vnc with putty and I was able to break the corporate firewall as the outgoing traffic is encrypted using SSH tunnelling via putty.
Next time you face corporate firewall problems preventing you to ssh to any system outside your lan in the internet the best solution is to tunnel your outgoing traffic via putty.
I struggled a lot for this...
Excellent link.
http://www.youtube.com/watch?v=cKhVFqSnhXw
Refer the above link and your VNC Remote Desktop issue by SSH tunnelling through Putty is done.Thereby you can bypass your corporate firewall.