AVI, as a widely used video format, to be exactly, a container format, can be found everywhere online and offline.
Since AVI is one of the most widely used video formats period, it would be important to convert files to avi for playback on most of the media devices.
You can Use XnView that is available for free to download to convert files.
Use a video converter software to convert flv files to mpg files .
that is impossible.
DAT files is commonly called VCD. you can a tool to convert this files to iPod files.
avi files are actually already video files.
Convert them to .mp4 files.
Some programs are designed to read special file formats and not others, for example Windows Media Player cannot open .ram (real audio media) files. Thus there are special programs to convert those files to .mp3 files so you can play on other programs
I had a crystal game where the saved files were ST1,ST2,etc. And i downloaded an emulator because i want to trade but here the saved files are SGM files. How can i convert my old files?
you do not do that
You can convert your music files from www.zamzar.com
Here is Video Converter Max that can convert your video files
http://myrightbrain.wordpress.com/2006/06/11/how-to-convert-mp4-audio-files-to-mp3-using-itunes/ There, follow the instructions and convert it. Or you could look at some programs.