DVD Burning Problem Uneven Burning and Shaded Rings

I am using Sony DVD writer870S. But while Burning a DVD I am facing some problems of
Uneven Burning & there are Shaded Rings visible on the DVD. However, from the same DVD writer I burn the DVD very fine.
I have recently changed my motherboard also.
Can anyone please help me regarding this issue.
I will be very thankful to you.
