If you downloaded a 'legitimate' movie, and now can't get it to play, that is probably a CODEC problem. There are many sites where you can find free CODEC packs. I use the one for Windows Media Player that I got at download.com. Download and install the CODECs and you should be fine.

If you downloaded a movie that, as you begin to play it, you see a message that instructs you to go to a particular site and download their player, then I hope you did not obey. If you downloaded and installed the Dom Player or one of its cousins, then you've probably infected your computer.

To avoid downloading harmful or simply mis-named files, you should check out Bitzi (described elsewhere in this Form). It's a website, (not something you download), accessable through LimeWire.