go to gta-sa.exe properties>compatibility mode>check run this program in compatibility mode for:below here select windows xp sp2 or sp3...i am sure it will work but now idea for 64-bit windows 7..
you should be install the game fine i have win7 x64 and no errors occurred, can you provide more info about you pc specs and what problems you're having when you are trying to install/run the game