So now the thing is need a new graphics card so that I can play starcraft 2 on my pc i barely use. I have no clue on what to even consider my price range is considerably low around 100$. Location looking to buy is India. Please Help.
The top performer is the 7750. The second is 6670 and last is the 440. All don't need the power supply connected to the card. And all these cards will run fine on your computer. You just need a PCI-E x16 slot. Which I think your motherboard has
And randomkid is correct, your CPU might not be able to handle Starcraft II.
Sorry just thought your PSU is most likely no up to using a 4850 as AMD recommends a 450 Watt or greater power supply with 75 Watt 6-pin PCI Express® power connector and yours is 300W so maybe a Radeon 6670 is a better option as a PSU would add another $40.
In this link you can see that even at 1280x1024 and medium details the cpu plays a big role. I play Starcraft 2 and actually feel the difference between 3.0ghz and 3.8ghz on my phenom II, which has way better per-clock performance than your Pentium D (meaning even if your cpu is at the same 3.0 or 3.8ghz, the phenom II will perform much better).
If you want to give your cpu a try, upgrade your power supply to something better (like the Corsair CX430 at 35$ or CX500 at 50$ on newegg) and get something like the HD 7750 (about 100$ at newegg). Then, if the cpu isn't satisfying you can upgrade to a new motherboard, cpu and memory later on.