Hallo ritesh, You are a bit vauge on your model no. so i couldnt look it up but i assume yours is a laptop? in which case a new graphics card is out of the question.
When Vista was first released i bought my first laptop which had the minimum hardware specs to run Vista Basic it also had a GE Go 6150, The Aero Index score was also 2.8
I managed to get the aero index score up to 3.0 by installing the latest chipset & graphics driver
fo my model from HP 24/7 Online support for HP's Home and Home Office Products - HP Customer Care (New Zealand - English)
So i promptly raced out & bought myself a Home Premium upgrade to install so i could introduce myself to aero.
What i didnt realise is aero requires 128mb of dedicated graphics memory and my Ge Go 6150 only had 64 mb of dedicated graphics memory.
To cut a long story short i kept forcing the aero thing and several Black screens later i landed up with a glorified doorstop that looks like a HP notebook
I am sorry if my story puts a damper on things but sometimes we have to be happy with what we have got