If you're like me and downloaded python and then ran the crack file in the same directory as Sai2.exe but it returns as no Sai2.exe is found, you went back and tried running the crack again and now all it says is Sai2.exe not found, hit enter to continue..
[My solution]
What i did was just uninstall python and reinstall. do the exact same thing you did and try running that crack file with the Sai2.exe in the same directory again, it should give you the prompt this time to enter the System ID. if not, run it a 2nd time.
Feel free to delete the crack afterwards. Hopefully that works for you!