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You said that your Bitnami stack is accessible in http://localhost:81 That is server name localhost, port 81.

However, you are trying to access http://localhost/test/kickstart.php That is server name localhost, port 80.

I am pretty sure Bitnami's Apache server only listens to one TCP/IP port at a time. Maybe you should try http://localhost:81/test/kickstart.php instead?

Also note that this is a server issue, not an Akeeba Backup issue. If you can't figure out how to use Bitnami you need to ask on their forums for assistance. We can help with our software, not your server setup. If you really want to know about my very well tested and known to be working Windows 10 server setup you can read about it on my blog. I have two flavours, the latest one using IIS (which doesn't support .htaccess files) and the older one using Apache (which does support .htaccess files). If you follow the older tutorial please use PHP 7.3 or 7.4 instead of 5.4 – apart from that, everything else is the same. If you do get in the trouble of creating yourself a decent local development server you might want to read about my tips and tricks on optimising PHP performance on Windows. In case you're wondering, I am using all three major Operating Systems for development and testing: Windows, macOS and Linux. My blog posts describe the setups I'm using on each Operating System. There is a substantial upfront time investment setting up your own local server, but you will save a lot of time and anguish later. If you're in for delayed gratification I whole-heartedly recommend following these tutorials.