Thanks Manik and Diwanshu.
the render times are 3 minutes on a pentium 4, 3.0 ghz, 1 gb ddr1 ram for a hd 720 image.
Thanks for the fed back,
actually i have lit the exterior wid pale blue lights, which shows when i turn of the interior lites,
but right now due to the strong interior lighting, i feel its not visible.
I will Recheck my lighting once again, Thanks again for the valuable feed back.