Need upgrade on my current system

[Shing10]

I have been using my dell inspiron 531 for almost 4 years. And i want to spend a little bit of money to upgrade it so i can play Starcraft 2 at medium setting. Here is the spec for my dell inspiron 531

http://support.dell.com/support/edocs/systems/inspd531/en/OM/appendix.htm#wp1149549

I am expecting to spend no more than $150 bucks

please help!!

 

[house70]

I would visit Newegg's site and decide on a video card/PSU combo that fits that budget. Highly recommend upgrading the OEM PSU when using discrete graphics.
Later on you could upgrade the RAM, as well, max it out. With these 3 upgrades you will have a new PC.

 

[AdrianPerry]

Adding a graphics card to the PCI x16 slot is likely your best option.

However the build spec you listed only has a 300w PSU meaning your options are fairly limited. I also have no idea if your PSU has a 6pin PCI connector in order to actually power a PCI GPU.