[DiapDealer]

There wouldn't be any problem installing over top, but I usually recommend uninstalling the old version first on Windows. Mostly for neatness. Some older libraries might not be removed if newer ones are being installed. I've never had it cause any problems--i just don't like old, unused files lying about taking up space. Regardless of which way you go, existing plugins and preferences will be retained (that's provided you use the uninstaller and don't manually delete anything).