where do I get the latest firnware for airport utility for windows 7?

The most recent version of AirPort Utility for Windows is AirPort Utility 5.6.1 for Windows - Support - Apple

7.7.2 is firmware for the new version of the AirPort Extreme or Time Capsule.

Whether it can be installed using a Windows machine is open to question since Apple states that you need to use AirPort Utility 6.3 or an IPad or iPhone to administer the new AirPort Extreme and Time Capsule.

AirPort Utility 6.3 is not available for Windows.

Firmware 7.7.2 indicates that you have a new version of the Time Capsule.

Apple has not provided a Windows version of AirPort Utility 6.3 for the new Time Capsule (or new AirPort Extreme). I don't know if AirPort Utility 5.6.1 could be used to configure the Time Capsule, but I doubt that it would work correctly....if it works at all.

The System Requirements for the new Time Capsule and new AirPort Extreme are shown below. As it stands, no Windows products would quality at this time. You'll have to use a Mac or an iOS device to administer the new TC or Extreme.

http://www.apple.com/airport-time-capsule/specs/

Setup and Administration

• iPhone, iPad, or iPod touch with iOS 5 or later and AirPort Utility 1.3
• Mac with OS X Lion v10.7.5 or later and AirPort Utility 6.3