OK What I suggest is to go Control Panel Device Manager, uninstall the Processor and let system autodetect itself this should solve the 1 Core Processor Problem
Perharps when Acer did the factory image they did it on a Single Core Processor so it will refuse to recognise a Dual Core Processor when the identical image is copied to your disk.
To boost your gaming performance update the nvidia drivers and DirectX
My blogs have some info on that as I am also using a AMD Processor, Nvidia Graphics Setup.
Acer Aspire 4530
AMD Turion X2 2.1GHZ RM-72 1MB L2 Cache
4GB DDR2 667MHZ
NVIDIA 9100M G
320GB WD BEKThttp://aspiregemstone.blogspot.com/