TV set always starts up indicating 420p. How do I get it to 1080?I have Bell expressvu HD

Is your cable or sat in HD(720p, 1080i, 1080p) over the air broadcast in the usa is in digital so it should start at the highest res available in your area

next are you using HDMI or composite for your cable or sat going into your tv if not your not going to get higher than 420p because A/V and S-video do NOT support HD

check your cable/sat box is it HD(high def) or SD(standard def) if SD going through cattv/attn in your only going to get 420p

now for changing the resolution its automatic it goes to the highest setting on its own

you can control the resolution through your cable/sat box, blue ray/hddvd player and other HD devices connected to the tv through the options menus of those devices BUT only when connected through

HDMI(supports 720p, 1080i, 1080p)
composite(supports 420p, 420i, 720p)
A/v and S-video(supports 420p)
cat tv/attn in(supports 420p, 720p, 1080i, 1080p) only supports what the tuner will do

i=50hz
p=60hz