I've already got the K-Lite Codec Pack it's still not working.

If you're running vista, I've had similar experiences where the codecs don't really make a difference. In that case I'd use VLC Media Player (http://www.videolan.org/mirror-geo.php?file=vlc/1.0.5/win32/vlc-1.0.5-win32.exe). It is free and will have all of the proper codecs and such built right in. The only real problem it has is with subtitles.

What video formats can it play and what video formats can it not play?

VLC will play most any DVD, AVI, MPG, MPEG, OGG, and a bunch of other stuff. Then again were you asking the OP?

Then again were you asking the OP?Yea. :)

Thanks infojunkie. I just switched used media player classic instead. However, do you know why I wouldn't be able to put in it in itunes?

Put what in itunes, your videos?