Purpose:
To see if I can do it. And well, people let me optimize their systems, I need to find a working solution so I don't need to help them too often. 
Goal:
A clean smoothly running computer with a minimal amount of effort. The aim is to use as few different software components as possible.
How to achieve the goal:
Seems reasonable to use a freely available software suite. That way I don't need to have too many pieces of software running, and reduce risk of incompatibility issues.
The Hardware:
An old FujitsuSiemens computer. As I won't do any numbercrunching tests, specs are not really important. I'll just see how it feels to use it. Will it get slower over time? A real user don't do benchmarking.
The Software:
The OS is Windows XP Home (Swedish OEM). Newly installed.
Did some research, and decided on the following things to start:
I also installed Mozilla Firefox and some stardock software to make it look good. (What can I say, it's important to me... It's a "real life" test, so I want it to be as I would have it. Along with the OS, these are the only commercial components I'll use on the computer.)
The Results:
... Pending ...
The computer has been up and running for a few days now, and I've had no issues yet. It's not been used very much yet though.
Additional Comments:
I'll keep you posted on any issues that arise while using the computer (If any. No news is good news. 
). I'll also post any changes I make to the installation of the computer.
Feel free to suggest things I should do. I'm not saying I'll do it, but I'll consider it, and perhaps someone else thinks it's a good thing to do if I don't. Keep in mind that this is a "minimal effort" attempt, so I'm not doing any advanced tweaking of any kind.
I'm also interested in how you'd go about doing the same test. What software would you choose? There are some altenative free software suites out there. Avast, AVG, Avira for antivirus. Glary Utilities for system maintenance. I don't really have a particular reason for choosing what I did, other than the fact that the IOBit PRO suite is really affordable at the moment (which isn't really a concern when running the free version 
), and Comodo has a good rep.