With some liveCDs you can try out the distributions that offer it. Debian
) is also one very good distro that runs well on old computers. Remember to get the 32bit ones.
If the liveCD boot well and you got the system running smooth that is a very good thing. The boot time can tell you a lot, lets say Ubuntu 11.xx take 5 or more minutes to load then is a definitely no, if some other takes like tops 60 seconds then oya !!! You don't want to fry the motherboard with too much load.
Remember you don't need to install the system with liveCDs to try it. Another thing that would be even better to don't stress your CD drive is to use USB sticks, install the liveCD in an USB stick, here
you can get the tool to do it.
I wouldn't keep that Ubuntu 11.xx on that computer. It is possible to do minimal and very tweaked install but you will need to learn how, if you are willing to get to that point it is a worth effort.