python - How do I run two different processes on Windows cmd from a python script?

Question

I need to run two different processes that will be running on two different cmd windows concurrently. These process are started from a python script. I tried this but it never worked.

import os

# first process
os.chdir("path/to/firstDir")
os.system("start cmd")

# second process
os.chdir("path/to/secondDir")
os.system("start cmd")

This script start the processes on different cmd windows but the second process start after the first has finished. I need both of them to run concurrently on two different cmd windows.

I'm on Windows 7 64 bit.