when the computer starts, it sais ''4 cores are activated'' . when it enters windows i open Task manager ,at performance and it only displays one core. And it really runs like if it is one core. for example at NFS undercover it runs at 100% and it doesn't run verry well and i'm shure 100% it's not the video adapter or the memory.
Make sure all 4 cores are switched on in your BIOS, if you are using windows 8 task manager shows overall utilization (looks like one core but it represents all cores use overall). You can switch this by right clicking the chart and going to change graph to: and then click logical processors.