Am Freitag, 16. November 2012, 12:52:29 schrieb Pascal Viandier:
> Hi TDE crew,
> I am running short on backup disk space so I decided to reduce the size of
> my home directory (I used KDE 3, then installed TDE and KDE4 for some
> programs, installed and removed many apps so my home directory has a lot
> leftovers). From this cleanup process comes my question: is it safe to
> remove the ~.kde3 directory if I work with TDE only?

should be safe, yes (if your trinity is rather current, e.g. 3.5.13 or newer).
to be sure, just rename your ~.kde3 to ~.kde3_old or similar (do this from 
plain text console, quit all graphic desktops before).
then see if everything still works as expected.
if yes -> delete ~.kde3_old

Werner