converting a file's format

does anybody know how to convert a ".ogm" format file into a ".avi" or ".mpg" or ".m1v" or ".mp2" or "mp2v" or ".mpeg"??? or does anybody know where to download a program to edit a video that is in ".ogm" format? (edit meaning something similar to windows movie maker so i can split up scenes) i tried to do this on windows movie maker but it doesnt support the ".ogm" format...if anybody can find another editing program that does support this file...that would be greatly appreciated if a link or information is provided. Thank you very much.