Rapid Environment Editor (RapidEE) is an environment variables editor. It includes an easy to use GUI and replaces the small and inconvenient Windows edit box. RapidEE 8.x supports Windows XP, 2003, Vista, 2008, Windows 7 & Windows 8 (including 64-bit versions). If you still use Windows NT or 2000, then use version 6.1. For Windows 9x or ME use version 2.1.
Rapid EE is portable freeware, so it's a great choice for a USB drive toolkit. Though changing variables may be a bit more system surgery than the average PC user cares to try, those who are more advanced will appreciate the significant improvements Rapid EE offers over the built-in Windows methods.