Try:
Start---> Run ---> msinfo32
or
Open a command prompt and run : wmic cpu get NumberOfCores
or
Start task manager and the number of square boxes in the CPU usage history will reflect number of cores on the system.
or
or
If you are an administrator you can check it via windows registry :
HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor
for each processor you will have:
[HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\0]
[HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\2]
or
Try coreinfo provided by Microsoft (application that runs on DOS)
If you still not able to determine how many cores you have then you probably have only one