The main cause of movies not playing on a computer is a codec problem. This is quite easy to solve. Follow the steps in this article and you'll find out that all your divx/xvid movies will play fine again. I recommend the following codecs and software:

Codecs/Filters:
- FFDshow Filter - A DirectShow decoding filter for decompressing DIVX and XVID movies

Players:
- BSplayer - Unique windows player for playing back all kind of media files. Its simple and easy to use.

Of course there are enough other codecs/filters/players out there on the big net.
But out of our experience this combination works out best.

Step 1: Cleaning the system To make sure your movies play correctly you need to remove all existing codecs on the system. This includes codec packs like NIMO and ACE. Do this by going to the add/remove software panel in windows. If you like to be on the safe side and do things properly, then firstly reboot the system before proceeding. If all of the codecs have been removed proceed to Step 2

Step 2: Installing the right software This part is really simple. Download the codecs mentioned above and install them with their default settings. No need to set any options. After you're done installing these things proceed to Step 3

Step 3: Testing the movies This is the moment we've been waiting for! Lets test whether it works. Fire up BSplayer (through the start menu) and open one of your movies. If you did all the steps above correctly your movie should play without any problem.

Troubleshooting If the movie is playing upside down, fire up the configurations panel of FFDshow through the start menu. Browse through the settings, all the way down the list you'll find a menu called "Miscellaneous". Click on it and tick the box saying "Flip video". Movie should play the right way up now.