GTA IV run to slow

Hello,
I am anoop I have every Requirement of GTA 4 but it run too slow can any own help me
did i need to bay 4gb RAM i have 3gb RAM

my Configuration:

OS Name Microsoft Windows 7 Home Premium

Processor AMD Athlon(tm) 64 X2 Dual Core Processor 4600+, 2411 Mhz, 2 Core(s), 2 Logical Processor(s)

Installed Physical Memory (RAM) 3.00 GB

display= NVIDIA GeForce 6150SE nForce 430


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