not sure if i'm posting this in the right place or not, but i have powerdvd xp 4.0. It works fine with capture from dvd and files like .wmv and .mpg. But when I try to capture an .avi file, it won't capture. I then installed ffdshow, and it let's me capture, but it won't capture full screen like it does with other files and in playback, the aspect ratio changes when i hit full screen. Is there a codec I'm missing, or need or anything?

Any help would be appreciated.

what you need is another player for avi files, like 'media player classic' which has its own capturing ability as well.
http://sourceforge.net/projects/guliverkli/

i downloaded media player classic, this one mpc2kxp6486.zip, and it plays the video, but the capture function is not clickable. is there a setting i need to change?

nope, 'file/save image' should work fine.