See attached link for instruction Here is a link that might be useful: WMP my default player

Use your head with this - a PC isn't a CD player, it's even better. Put any and all your CDs into the PC just once, rip them (transcribe the music files into computer files), and then play them an infinite number of times using the sound files stored on your hard drive. Either WMP or Itunes will do the rip. If the CD can be read from one PC and not the other, rip the CD on the working PC and then move the files to the other. Or, rip all the working files on the "bad" PC, and use the working PC to rip and transfer just the one non-working file. A concept that's hard for some to grasp - if you're trying to do something and it doesn't work, it's unlikely the solution is to do the same thing over and over again. Instead, try something different.

Here's an explanation lifted from a webpage: A codec is software that is used to compress or decompress a digital media file, such as a song or video. Content creators use codecs because a compressed file takes up less storage space on your computer and can be transferred across the Internet more quickly and smoothly. When you play a digital media file, Windows Media Player uses a codec to decompress the file. Codecs are used to create and play nearly all music or video files on your computer or on Web sites. Q.Why do I get a message that says my computer is missing a codec? A.You are probably trying to play a file that uses a codec that is not on your computer. When you try to play a file that uses a codec that is not on your computer, the Player tries to download the codec from a Microsoft server. If the codec is available, the Player installs it on your computer and then plays the file. If the codec is not available on the server (for example, because the codec wasn't created by Microsoft), the Player displays a message that your computer is missing a codec. If you are connected to the Internet, the message usually has a Web Help button that you can click for more information. If the Player can determine which codec you are missing, when you click that button, a Help topic is displayed that contains a link to WMPlugins.com, a Web site that lists a number of codecs that are available to download. The MPEG-2 and DivX video codecs and the ACELP.net and Ogg Vorbis audio codecs are examples of codecs that are not included in the operating system or the Player by default. Q.How do I find a codec? A.When trying to find the right codec for a particular file, you can use WMPlugins.com or other Web sites. Typically, you should start with WMPlugins.com first. Recommend that you use caution when installing codecs that aren't listed on WMPlugins.com or Microsoft.com. If your computer is running Microsoft Windows Millennium Edition or Windows XP, we recommend that you set a system restore point before installing any digital media components. This enables you to return to your original system configuration, if necessary. If you get a message that you're missing a codec when you try to play a file, click the Web Help button on the message. In the Help topic that is displayed, click the link to WMPlugins.com. If you know the name of the codec you want to find, you can go directly to WMPlugins.com Codec. If the codec is listed on WMPlugins.com, follow the instructions on the page to download and install the codec. Q.Does the Player always try to download codecs automatically? A.It depends on several factors. To ensure the Player can try to download codecs automatically, you must have Internet Explorer 3.02 or later installed on your computer, maintain Internet access while playing the file, and your Internet security should be set to Medium. In addition, if your computer is running Microsoft Windows NT, Windows 2000, Windows XP Professional, or Windows Server 2003, you must be logged on as an administrator or as a member of the Administrators group. Finally, do the following: On the Tools menu, click Options. On the Player tab, select the Download codecs automatically check box. If you use the Player in a work environment that is managed by a network administrator, you might be restricted from downloading and installing software from the Web.

It's not on a site. The video was taken with the computerized microscope named Digital Blue. (It's a "toy" scope for kids but big kids like to play, too.) The files played on the original computer when I used the Digital Blue software. I exported the files from the Digital Blue folder then, once exported, copied to my thunb drive so that I could transfer to my computer. As I said, they won't play on my computers (both Vista) even though they both play avi files from other sources. I also tried to convert to another format via zamzar but received error message unable to convert. (Sorry, I don't recall precise wording. Could try again if it's important.)