Why can't ripped movies import to into iTunes on Windows XP when they work on Mac? I am unable to copy movies or videos into my iTunes library. I have had the concerned videos converted using Handbrake (version ??) with Apple presets but still when I try drag and drop to iTunes (10.1 on Windows XP) it shows no error (like "cannot be played" etc) and neither does it show up on the list.

I can copy songs/ebooks/apps got a problem with video only.

So I updated to iTunes v 10.5.3 still can't drag drop video/movies. I even tried adding the files to the Automatically add to iTunes folder (as suggested in one of the comments) but got a Not Added folder. The files work when copied to the library on a friend's, so I can't tell if the problem is iTunes or Windows XP or my computer.

Am I missing something?
I have been facing the same problem with iTunes (both 10.5 and 11). You need to upgrade to iTunes version 10.5 or 11, and you would need Quick Time to play older media or videos.