I don't know about your information being kept secret, but try this site:
http://media-convert.com/convert/
I don't know how "safe" it is, but I know it is free and you can convert any file type to any format that your iPod, iPhone, etc. will support...
For example, say you downloaded a video to RealPlayer, and it is in an ".flv" format. (Flash Video) Just go to media-convert.com, click "Browse" (on their homepage), search your computer for desired file you would like to convert, and open it.
The site should automatically detect what type of input file you chose to convert, but you may have to choose the output format. (A video file such as "Flash Video" may best be supported by an "avi" extension, or format, for example.)
Click 'OK', and within a very short time your file will be successfully converted to the format of your choice. Click on the file name and choose "Save" in the options box that appears. Then choose a location on your computer to save it in and a name for the file. Click "Save", and in a matter of seconds your file will be successfully formatted and ready for you to sync to your portable device that supports it's file extension.
I hope this helped!