Installing Frozen Throne 2 times

Hi all, I am trying to install Warcraft III/Frozen Throne another time on my computer, so I can easily use the english WE. However I also want to keep my previous italian copy installed on my pc. Is there a way to install it twice (I also have both english original CDs with their original cd-keys)? I tried to copy all the "Warcraft III" directory in another place changing only mpq files, but there are problems:
1) Cannot patch the game;
2) Cannot copy the english Frozen Throne mpq file (on the standard Wc3 CD there was the war3.mpq file on the main directory, but on the Frozen Throne's one there is not the war3.mpq file).
Any help will be appreciated. Thanks.

Even though it is not directly related, I think that this fits better in editing tools.

I don't know incredibly much about this, but Warcraft III uses the registry to find the path of the program, to be used for example when you are trying to update that game. So that is [a part of] the problem.

That is not a problem, you can change the path when you need to update.

Install the english version and copy war3x.mpq from the directory u installed to.