There is no sense in upgrading this old machine.
Also didn't pick any card with only 256MB.
If you still insist try with Radeon 6670. i.e:
@69 USD => 50USD after rebate GIGABYTE Radeon HD 6670 http://www.newegg.com/Product/Product.aspx?Item=N82E16814125403
It will big difference from integrated.
Please tell your budget and what else you want to upgrade?
Could you also check how much power your PSU have?
Is this CPU normal Pentium 4 or dual core?