Problem with codecs

[Izumi]

Hey I got a problem with codecs, if I setup divx or any other codec it doesn't show picture but I can hear the audio of the file. I got installed only xvid codec and it plays some of the .avi files but the rest needs the divx codec. Somebody told me I got to format the windows and install again so I can be able to play the files. Is there any way to fix the problem without format? I tried to play the files with BS Player, Winamp, VLC Player, Windows Media Player Classic, Micro DVD and Real Player Gold but I couldn't get it working. Can somebody help me fix the problem?
Thanks in advance.

[LT. Columbo]

you sure these are in fact REAL files and not some type of fakes?

[Izumi]

Yeah becasue these files were playing before