I am able to connect if i set router as unsecured
Have you tried both levels of encryption using WEP as well as WPA?
Have you tried setting the Router to G only?
Have you tried a different Channel on the router (1, 3, 6, 9)?
What happens when you try to connect? You say it sees the Wireless network, when you type in the security key or passphrase, what happens? Do you get an error or does it just sit there forever attempting to connect or acquire an IP address.
If it seems to continue to try to connect without error then try disabling IPv6 in the properties of your network adapter.
Make sure you have the latest driver for your adapter from here...