It's not a good thing because if I face this same problem again I won't know how to solve it.

Maybe in my last try I seem to remember that I entered "999MB" as a size instead of "2". I entered "2" before because I thought this file would be a settings file with text inside, but it's more like a sort of user partition, isn't it ? Could it be the reason why it did not work ? If so, it should not let the user enter a number too low to work.
"mnt/sda1/porteus/modules/" is still read only though. When I install a webbrowser, it tells me to move it from "tmp" to "modules", but I can't.
edit: I got to do it with "sudo cp " and it's still there after a reboot.
Many texts are still in english though, maybe the french language pack is not 100% translated.
Another question : how can I set numlock on at startup ? I do not find this in the settings.
Yes, I am trying a few lightweight distros in virtualbox to choose which one I will install on my father's very weak laptop which is totally dying crushed under windows's fat ass... Porteus is my favorite one by far by the way, so fast, so light, yet lacks nothing.