There is another lightweight Linux OS you can try and that's SAM Linux, download, screenshots, etc from here:http://sam.hipsurfer.com/news.php
Once again this is a 'live' CD which you can install if it plays nice on your rig. I had this running for three months earlier on this year installed on an old 600 MHz AMD machine sporting 128 MB ram, and it was perfectly usable as basic computer for surfing, email, and simple office tasks.
SAM Linux uses the Xfce 4.4 desktop, which is nice and light, less demanding on the computer and brilliantly useable. I realise your candidate computer is rather less powerful that the one I installed SAM Linux on but the SAM developers claim that their Linux OS can run on a mere 300MHz CPU or less, so maybe it's worth a try.
You do, of course, need to make sure that the computer hardware you intend to install to is in good order, but that applies to any installation of any OS on any computer.