GTA should it play on

I have GTA IV on pc.
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My spec of computer is:-

Intel Core 2 Duo E6600 running @ 2.8GHz
Corsair matched pair ram 1GB each = 2GB
Asus P5QL-E Motherboard
200GB Sata HDD (Samsung)
ATI Radieon HD 4830 512MB GDDR3
2x DVD+RW DL
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It meets the minimum requirements.
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But when i play it.

If i am in a car or even walking it is jittering.

I have had it running on Windows Vista and Windows XP no problems at all.
But since having installed Windows 7. It has just brought a load of problems into playing it.

Your Help Is Appriciated

Thanks

G4V1N
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