Mandriva is an RPM distribution and commands related to packaging won't
work. Plus it is built differently so things may or may not work the same
way or be in different places. It is best to keep RPM and Debian distros
apart in your mind. Ditto for Fedora, but it is harder to configure due to
SE Linux permissions and it is more geeky to begin with.

I think that antiX is still supported. As for MEPIS, what version did you
try? If it is 8.0 then it is worth trying 8.5 which uses KDE 4.x instead of
KDE 3.5.

Compiz Fusion requires a 3D graphics card. It uses compositing and takes
system resources to do all of that nifty stuff. It works on my netbook with
1 GB of RAM, but I shut it down because it slows things down too much.

I kind of get the feeling that not too many people have your problems. It
makes me wonder about your hardware and some of the things that you may have
tried in the past that may be coming back to bite you.