ప్రత్యుత్తరాలన్నీ (2)
Not within Firefox. That's a Windows issue. Can't help you myself, I'm still on WinXP.
Try - http://www.sevenforums.com/ - the best support forum for Windows 7 that I have seen.
Some laptops have a hardware switch on the outer case.
Some firewall programs have a switch that can shut down all outside contact.
Windows: Control Panel > Network and Sharing Center