Please tell me how to set up simple computer system

@faster24 do you plan to connect it to external speakers, headphones, or a stereo system?

Honestly using a PC, especially a 13yr old one, is not going to be very good sound wise. And personally I would toss any computer over 10yrs old. Any streamer will be much better. 

@kofibaffour

+1

We need to know to what? An external DAC?

Budget?

Powered speakers with an internal DAC would be simplest if you are ok with running a wire from the laptop to the speakers. If you don't want to run the wire then networked powered speakers would be the next best way to connect to the laptop

I suggest dropping the MacOS and installing Linux. You can make Linux a fit for purpose operating system that focuses on streaming. Even an older device is plenty fast given the right configuration. That is pretty much what every commercial streamer is anyway.

Below is an AI summary of the install process. This is a link explaining how to build the device for streaming. I have done this with a very humble Dell E6510 and is does quite well. Albeit I don't stream a lot, but when I do I am not disappointed in the results.

https://www.24bit96.com/hifi-music-server/bitperfect-linux-with-mpd.html

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Installing Linux on a 2012 MacBook Pro is possible and can be a good way to give the older machine new life, especially if you're looking for a more lightweight and efficient operating system. It involves creating a bootable USB drive with a Linux distribution, booting from the USB, and then installing the chosen distribution. However, you may need to install drivers for Wi-Fi and other hardware. 

@jbs 

You would have to technically explain how a computer - old one vs. new one - makes music sound better?

If your music resides on a hard drive and the computer is merely passing on the X's an O's to a USB cable (which I have found does make a difference) then I am stumped at how that would be of importance.

The only technical aspect I am aware of that may come from the computer is jitter. However, most DAC's nowadays incorporate jitter reducing remedies so that is no longer an issue. It did give rise to the "jitterbug" for a number of years.

I have read that some here state the software they use (typically Roon or jRiver) has an effect on sound, but I assume that is when streaming or accessing music over a network. Using Windows Media or iTunes to play music that resides on the local computer hard drive should have no effect on sound.

I have used a few computers and there is no difference in sound. If anyone asked me I would tell them an old computer is just as good as a new computer when playing local music files. Dedicating a computer (Jukebox computer) is recommended as I could see a whole host of issues if one is playing music on the same computer they utilize routinely. 

I think any recommendations need to be based on more information. But it doesn't seem likely that there is a high end audio system involved here. Otherwise, discussions of how much difference JRiver, vs iTunes, vs shutting down background jobs... vs a dedicated streamer is going to make. 

It is sounding like connect USB to some input device and choose the output device on the MAC. 

I agree we need to know more to be really helpful. Things that are important to know include:

1. What other components are involved so we can determine where on the spectrum this solution needs to sit.
2. How computer savvy the person is and/or if they have a friend who can do some technical heavy lifting.
3. Where streaming fits in with other medium; will it be a primary source or more one to explore new music?
4. Will the streamer also stream .flac files ripped from CDs? If so, how many CDs worth?

I agree, old/new, it’s just bits to the DAC

I learned about using USB out of my PC to a Topping D10 DAC, I stream lots of audio and music videos in my office, the most important was the physical re-arrangement to get great imaging.

https://www.amazon.com/dp/B08F54TT79?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1&th=1

I needed a USB 3.0 extender cable to put the DAC on the shelf below my amp

https://www.amazon.com/dp/B00P0ES0YE?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2&th=1

Sit dead center of speakers and monitor