Windows Environment Variables

Check

REG QUERY HKEY_CURRENT_USER\Environment

REG QUERY HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\"Session Manager"\Environment

or

REG QUERY HKCU\Environment

REG QUERY HKLM\SYSTEM\CurrentControlSet\Control\"Session Manager"\Environment

You can also launch System Properties, choose the Advanced tab and click Environment Variables...

sysdm.cpl

Or launch the Environment Variables screen directly using...

rundll32 sysdm.cpl,EditEnvironmentVariables

Set Environment Variable

SETX VARIABLE "value"

Alternatively use

regedit

or

rundll32 sysdm.cpl,EditEnvironmentVariables

or, to also be able to Edit the System Environment Variables...

start-process rundll32 sysdm.cpl,EditEnvironmentVariables -verb RunAS

Unset Environment Variable

SETX VARIABLE ""

REG DELETE HKCU\Environment /V VARIABLE /F