Hello Hiren, and welcome to Seven Forums.
Using the tutorial below, double check to make sure that the
Number of processors box is unchecked. This way Windows 7 will be set to use all available processors.
Processors - Limit Number Used by Windows 7
You will probably also need to reset your CMOS or BIOS to factory defaults to toggle it to recognize your new CPU as well.
Hope this helps,
Shawn