"Unless you know how to change your hardware
acceleration settings (to none) on the dvd 
program your computer has you wont be able to 
take a screenshot with the print screen 
button."

That doesnt work all the time with newer OS's. I 
have XP and doing that did nothing to let me 
take screen shots on any program i used to play 
dvds, its still just copied a black screen. Your 
best bet is to get PowerDVD, you can buy it 
pretty cheap.