@bajaj151. hmm. can you post more detail like speed of both the sticks and look for error logs in windows.
if the OS works fine with 1Gb model, either the second module is faulty or the second ram slot is fault. try different things like test with 1gig stick and then only with 512gig stick and then placing gigs in different ram slots.
btw, what is the model number of you mobo.