Best bet is just run whatever OS was shipped with the computer when new and install the updates and patches for that version;it will continue to run all the programs it originally ran.When you have new needs,then buy a new machine with the latest OS pre-installed;it will save you money and time.
Same basic principle applies to MacOS and others;as OS feature list grows so does requirement for more ,newer hardware.
I know of control systems now running on high-end P4 boxes that originally ran just as well on a Win 3.1 486 box.The production machine ,its sensors and motors simply don't require much computing power.
Americans spend a fortune replacing a lot of things that were still performing their functions economically.just to have bragging rights "I got a new "xxx".
Best bet is just run whatever OS was shipped with the computer when new and install the updates and patches for that version;it will continue to run all the programs it originally ran.When you have new needs,then buy a new machine with the latest OS pre-installed;it will save you money and time.
That is my approach as well. A friend built a new box for me in December '08. I bought a new XP disc and installed XP. I have much better things to do with my time than start from scratch installing and replacing files if I wipe my current HD clean. I'll save upgrading my OS for when I upgrade my machine, or get a laptop.