Desktop environment in ubuntu

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http://askubuntu.com – I have a dell optiplex gx270 that I wanted to run ubuntu 12.04 on, after installing it on virtual box it was very sluggish and was using 100% CPU so I switched the desktop environment to lxde but it installed openbox and gnome/openbox is it safe to remove them is it also safe to remove unity? If it is safe how would I remove them? Thanks (HowTos)