Usually to read old media, you wouldn't start by building a PC. The first thing is the hardware that works with the media, for example a reel to reel tape drive, 8, 5 1/4 or 3 1/2 inch floppy drive, tape drive for old cartridge tape formats etc. Then you look at the interface needed to work that old hardware, then you look at what computer you need to host that interface, then an operating system, then the tools needed to get to and make sense of the data.
Luckily the OS part is pretty easy. Linux has support for all sorts of weird and wonderful interfaces right out of the box. It's also usually packaged with all manner of powerful tools good for getting data off old media.
It's getting old hardware to actually work that'll challenge you.
Scientists will study your brain to learn more about your distant cousin, Man.