This has to do with IE 8, not Windows 7. Simple solution is Firefox
(Settings are much easier to change.) But I believe you can change IE 8's settings to stop that popup. From within IE, click on Tools>Internet Options. Click on the "Security" tab, and then make sure that the "Internet" zone is selected. Then click "Custom Level..." Underneath "Settings", scroll down to the "Miscellaneous" section. Within "Miscellaneous", find "Display mixed content". It should currently be set to "Prompt"; change it to "Enable". Click "Ok" out of all the dialog boxes to make sure that the setting is saved. You should be set! (I hope; if that doesn't fix it, it's beyond me.) Good luck!