Enter Koush’s Universal ADB Driver for Windows. Koush is the developer behind popular apps for Android devices including ClockworkMod Recovery, Carbon file backup, and ClockworkMod Tether.

If Android Debug Bridge fails with error ADB is not recognized as an internal or external command, operable program or batch file, do this.

ADB (and fastboot) is no longer an issue on Windows 8 thanks to this driver. Koush didn't do it alone, though – this has been a sort of "project" within the community for some time now.