Thank you for using our answers forums. Sorry to hear that you are having issues connecting to your Slingbox. You can try a few things to try to make the Slingbox work using the Windows 7 computers. First, you would need to make sure that you are running supported browsers. You can also try to clear the cache and cookies on your browsers. It may also be an issue with your firewalls not letting the Slingbox through. These articles below should help you further.
Some Internet security and personal firewall software may interfere with your Slingbox setup or SlingPlayer
The Sling Moderation Team