I mostly use an old XP laptop. Maybe 10 years old? But putting trades can be done on any computer or with phone.
I willl usually run some scans on the markets once a week.
I do a lot of my research-making indicators-systems etc. on 2 old XP desktops 10 or 11 years old, and 1 older windows 98 machine.
The software I use is TradeStation and ThinkDeskTop. Both FREE! I like FREE! ;)
And you can program anything you can think of with them.
If you can dream it up and explain it. It can be programmed and used!
But will most likely upgrade next year when the new windows software comes out.

In our bussinesses we like to upgrade computers every 2 to 3 years, depending on the software needs.

Of course like everyone else we auto backup hard drives.