Branch = copy - no central repository of branches?

[Paul Moore]

I'm thinking of moving over to using some form of VCS for my personal
projects. One of the distributed VCS systems looks like a good idea
for the way I work. I'm looking at a couple, to see which suits me
best.

One of the ones I'm looking at is Mercurial. It looks nice and simple,
and fits how I think about things (and I like Python, so that helps,
too!) But one thing confuses me. The idea that to create a branch you
simply create a new copy of the repository (hg clone) seems to me to
be logically the same as the way I currently work - if I want to try
something out, I copy the directory.

But where's the protection, then? I copy the directory, start fiddling
round, commit some changes, then lose the disk (in my case, that's
often "lose" in the literal sense - I can't remember where I put the
directory I was working on branch XXX in! :-( ) There's no central
repository with all the branches, so I've lost all that work!

Have I missed something? Is there a way of maintaining multiple
branches within one repository, so that I can have one central backup
point for "everything"?

Thanks,
Paul.