GTa IV Freez

Pls Help me sa freeze tout le temps ma config :

Ma config :
CG: ATI display adapter (0x9505)
Video Ram :MB 512.0 MB
Pixel Shader version 3.0 3.0
Vertex Shader version 3.0 3.0

REanimator Extreme Edition
Version 15.10-24.12.2006
AMD Athlon9™64X2Dual
Core Processor 4400+
2,30 GGZ , 2,00 Gb de Ram

Asus EAH3850 series (512 Mb )

Asus VW1935 [19''LCD]