I don't want to bother Florian again, so after spending some time googlin' around and a little bit playing with portable apps I've realized I can make it by myself.
And now I got it, a portable MP3Tag installation!
I'm now testing and working to make it distributable, I mean a clean install with default options; I will post it here in the next days if Florian agree with this portable installation and if I have enough space to post it here (the size of the autoextracting file is 1150 Kb at the moment).
I may send a copy to Florian, if he wants to take a look; I've used some stuff from the site PortableApps.com to make it work without modification of the program code, but I don't like a lot to play with registry settings; so if Florian may reconsider the use of a INI or XML, or whatever he wants to use to save settings, I think this kind of installation will be more stable.
Anyway it seems to work even with settings saved in the registry and export, web sources and actions in %appdata%; my portable install uses a local copy of the registry and a portable appdata dir, so you can port from one pc to another your preferred export, actions ecc.
The only thing not ported is shell integration.