Hi,
I think i figured out the trouble.
Actually when i connected the UNO board to my laptop, it does reset each time and even now.
I tried connecting the UNO on my desktop PC, here it is it does not reset at all.
i have tested it for maybe 1 hour now, and it seems to be fine.
So i think my source prob was my usb. . .
Any suggestion upon how i can solve this issue on my laptop . . . 
Still atleast i know my UNO is alright till now.
thanks to everyone who help and gave me the support up to here .. 