Hi P A F B
Why not load one of the Unix/Linux distros?
In my experience, those (old) XP machines work a treat.

Especially when you delete Windows
Try Ubuntu [Ubuntu.com], it will not take long to download/install.
You can then run the linux versions of Firefox and Thunderbird, Libre Office.
ALL FREE!
[ see also
http://www.linuxlinks.com/ ]
There are some good linux educational sites/literature around.
My personal favourite mag is LinuxFormat (LinuxFormat.com)
You are NOT too old to carry out the task, especially as you have done something similar before.
[ Taught yourrself that is ]
You have been given a machine which stands you in at nothing.
It therefore also does not matter if you make a mistake (or 5).
Go on!

Ray