NVIEW second montitor fullscreen. Sometimes works.. why?

My set up:
-have a Gforce 4 Ti4200
-My cable set up to my computer is perfect.
-My desktop spans from one monitor to the TV with no problem.
-(important) When i play a video it will display as 'full screen' on
tv monitor. This alows me to control things on monitor 1 while monitor
2 plays just the video full screen.
My Problem:
-Some videos will only play and not fill up the second monitor. Other
video files play and they'll go to "full screen" with out a fuss.
-How can i get all videos to play full screen.
Clues:
-Some videos work even with the same file extendtion (such as avi,
mpeg, or mov) and/or the same codec (i usually just save videos as "no
compression" but some times i save them with the diffent codecs
available)
-I'm not very smart.

Help me please! i really need this function so i can record diffent
videos i make to tape at diffrent times while recording at the same
time. Other ways cause me to stop working when recording causing me to
take longer on a project. Thank you, to anyone who reads this.