Don’t worry, there is no stupid question :)

You have a masterkey directory and one CREDHIST file per user account. For each user account, they are both located under Application Data\Microsoft\Protect (for XP) or AppData\Roaming\Microsoft\Protect (Vista & Seven). SYSTEM account also has masterkeys (but no CREDHIST), located under Windows\System32\Microsoft\Protect

Be aware that they are hidden and system files so they are not displayed by default on Windows (could be configured in explorer).