As Aaron pointed out, you can use the Set command to change the Temp and Tmp
environment variables. But these are on a per user basis, and would need
to be re-done after each boot/logon.
You can also change these in System properties, Advanced, Environment
Variables and make these changes permanent.
The affected Registry keys are:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session
Manager\Environment
and
HKEY_CURRENT_USER\Environment
