Are you trying both programs or just one of 
them?  I have my computer defaulted to real 
player eventhough I have other media players on 
it.  When I create the AVI and select the scene 
I want I click the run button on the Max DVD/AVI 
contverter and it'll ask questions about MPegs 
and such.  I just click the ok button without 
selecting any files.  So it defaults to what it 
wants.  When I have my AVI I click on it and it 
opens real player.  The real player screen size 
is quite small.  It doesn't take up the whole 
computer screen.  I then open up screeh cap pro 
and it asks what you want a shot of.  One of the 
options is to take a screen shot of whatever 
window is open at the time.  So I click that 
option and then click the real player window 
that is paused so that it knows the take a 
screencap of the real player window.  It then 
shows up on screenshot pro and you can save it 
as a .bit.  I then go to adobe to convert it to 
a jpg.  Hope this helps out a little.  If not 
you can drop me an e-mail or we can chat on AIM 
or MSN preferrably and we'll figure out your 
problem together.  You may have downloaded the 
wrong program in the screenshot pro.  There are 
many out there.  If this doesn't help then let 
me know and I'll see if I can't find the link of 
the program that I have.  ^_^
Good luck