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To answer your question, yes and no.
Your Inspiron 530
does have the required PCIe 16x slot so it is capable of using a 4850.
The power supply, however, is only rated at 300w.
As the 4850 Requires a 450w PSU
with a free PCIe 6 Pin power plug, you would have to upgrade this component also.
If you decide to do so, look into a Corsair, Seasonic, PCP&C, Enermax or Antec Earthwatts 450w+ PSU.
Avoid a cheap PSU if at all possible as they are underpowered (rated to output more than they really can) and are prone to failure.
Another alternative would be the 4670 which is designed to run in a low power system.
It will still give you a massive upgrade from your current IGP and should run with your current PSU.