If checking the laptop before buying when the sticker is missing, open Windows Explorer and right-click on “Computer”, select Properties. Or go to Control Panel - System.
If checking from within your app for hardware requirement, you can check the Registry:
If you subscribe to xDev then you might want to read the Multicore primer series. Windows is covered in issue 14.3 and 14.4.
But in short (as Norman said) WMIC is the way to go.
WMIC is available for WinXP Pro SP3/Win2003 and upwards (though there was a hotfix to make it run on WinXP Pro SP2 - see https://support.microsoft. com/en-us/kb/936235)
Just be aware that due to system policies not all cores might be available to a user (on multi-user systems the number of cores you are allowed to use is set by the admin).