Sometimes you would like your Sims to be in the "new state" again, as if you just bought it.
Off course you can delete all your expansions and re-install again, but this is quite a job when you are the proud owner of all expansions ans stuff-packs.
Simply remove the folder The Sims 2 - see backup - and startup your game.
A new folder The Sims 2 will be created and all your old Sims, Houses, Downloads etc. are disappeared.
Simple but very effective !