I'm also having this problem, also Windows 7.
I’ve just released itch-setup v1.24.0, which no longer uses CoIncrementMTAUsage and should work on Windows 7.
You can download the latest version from https://itch.io/app, as usual.
Please report back whether it does or doesn’t work for you on Windows 7. (If you’ve gotten itch installed in the meantime - it’ll just verify and repair your existing install, you won’t lose any data).