>I have a pc with XP Pro installed. This pc has a CD drive (not DVD). I connected an external DVD drive (via USB) to this pc but when I try to play a DVD, I get a message something about "DVD Decoder" not installed. Is DVD Decoder something you have to buy or it can be downloaded free?
>
>Thank you.

Dmitry, see
http://techrepublic.com.com/5208-6239-0.html?forumID=49&threadID=159459
http://www.microsoft.com/windowsxp/using/setup/expert/bridgman02april15.mspx
http://www.microsoft.com/windows/windowsmedia/windowsxp/dvdplay.aspx

for more info