Windows – How to re-source the environment variables in a command prompt in Windows

To make the environment variable accessible globally you need to set it in the registry. As you've realised by just using:

set NEWVAR=SOMETHING

you are just setting it in the current process space.

According to this page you can use the setx command:

setx NEWVAR SOMETHING

setx is built into Windows 7, but for older versions may only be available if you install the Windows Resource Kit

There are two sets of environment variables: user and system:

The system variables are the same for all users on the machine, and require Administrator privilege to change.  The user variables are individual to each user, and can be altered freely by the user.

For most variables, if there are a system variable and a user variable with the same name, the user variable simply overrides the system one.  But PATH is a special case — the value of the variable that is set in CMD is the user variable appended to (the end of) the system variable (with a semicolon (;) interjected, if necessary).

It looks like you made a common error — you copied your complete PATH value into the space for your individual PATH variable in the environment variables dialog box.  (Or perhaps some buggy program did this for you.)  This resulted in the system PATH value being duplicated in your individual PATH variable, so now you get the combined / duplicated value whenever you start a Command Prompt process.  The solution is simply to edit your individual PATH variable to remove the first 14 entries (i.e., everything but K:\sw\Git\cmd).  Those 14 directory names are in the system PATH value, so you will still get them in your PATH value (but only once).