环境变量的注册表位置
另外说一下环境变量在注册表中存放的位置：
system environment variables: (machine)
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment
user environment variables:
HKEY_CURRENT_USER\Environment
system environment variables: (machine)
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment
user environment variables:
HKEY_CURRENT_USER\Environment
