The above posts are correct about which equipment types have inflight entertainment capabilities - 73G & 738 (700s and 800s), the 757s, and obviously the 777s and DC10s.

I do not go to PHX very often, so I would have to check the electronic timetable to see if there are any 73s on that route, but if there are I am sure they are 733s or 735s, as I can tell you for sure that that flight is NOT long enough for a movie. I do a lot of IAH-SAN and IAH-LAX, and those flights are just barely long enough for movies. The IAH-PHX schedules at something like 2:35, which is not long enough.

If you are going to CLE or EWR, I'm not even sure if CO has direct flights or if they are all HP, but pull COs Electronic Timetable down from their web site - it's really great if you have a Palm VII, but there is a version for the PC - and you can see the City to City timetables, which do show equipment type. Look for 73G or 738.