Sure they can ....
480p is progressive mode DVD display.
Not all TVs, but some can do 480p and not any higher (so no HDTV modes)
480p isn't considered HDTV but SDTV

TV's which can only display 480i (720*480 interlaced) and/or 576i are called SDTV's.
TV's which can also display 480p (720*480 progressive) and/or 576p but not any HDTV resolutions like 720p and 1080i (1280*720 progressive and 1920*1080 interlaced) are called
's.
Thraxen beat me.