This friend of mine had an idea to make a program witch would be used to manage large numbers of mp3 files, with the ability to change their ID3 tags all at once. This would be usefull if you wanted to divide your mp3 music ino genres etc.
Now he gave up on the idea, but i still want to try and do it.
I just wanted to know if there is someone who can point me in the right direction. The main issue here is accesing the ID3 tags. I do not know how to extract the tag from an mp3 file.
All the other stuff won't be a problem, I think.
Thanx in advace, guys.

Either use a library like FMod (only one i know off the top of my head) or write your method for extracting the data. It's not too difficult to write an ID3 tag reader, but it takes some work to support all the versions.

You can also search here for information on the format:
http://id3.org/

They also have a mailing list if you have questions. I wrote an ID3 tag reader in Java awhile back, but it never supported all the formats. I later just switched to a library that was already pretty developed. But as far as C# goes, I haven't done much research on the topic. I will have to eventually because I also will be starting a similar project.

I just found this library developed by Novell, looks like its just what you're looking for.
http://developer.novell.com/wiki/index.php/TagLib_Sharp