i h ave a 5850 and only a few algo's are still optimized for that gpu, blake256, cryptonight, quark, qubit, LYRA2REV2, Keccak are mostly where you will do good.. having only 1gb of ram hurts it when you want to do DAGGER-HASHIMOTO
I used to mine with 5850 but I sold all. Just because they are less efficient in mining than the newer cards.