Why bother downloading them when they can be got free as streaming media? at least that way there is no fear of virii.
but to keep to the thread, try using veoh or stage six - with both of these you have the option to save the vid to your hard disc if you want - or just to watch it streaming.
they are here:
http://www.veoh.com/ http://stage6.divx.com/
with stage six you will have to install the divx codec if you don't already have it - but it is worth it cos the quality is as good as dvd.
of course the problem is finding the film that you want in the first place.
good places to look are: