XP 支持工具（可以从您的 XP CD 安装）附带一个名为setx.exe：

C:\Program Files\Support Tools>setx /?

SETX: This program is used to set values in the environment
of the machine or currently logged on user using one of three modes.

1) Command Line Mode: setx variable value [-m]
   Optional Switches:
    -m  Set value in the Machine environment. Default is User.

...
For more information and example use: SETX -i

我认为 Windows 7 实际上是setx作为标准安装的一部分提供的。