Can't get .vcxproj files out of git

[Alhazred]

I am programming a software in C++ on two PCs running Windows with a slightly different Visual Studio configuration, but both still compatible with the project.
To keep all in sync I'm using Github and because of the slight differences I want to keep the .vcxproj files out of the synchronization, but I'm failing.
Inside all the .gitignore files I have these two lines
*.vcxproj
*.vcxproj.filters
and each time one of the vcxproj file is updated, it wants to be committed.
Its worth saying that it was not like this from the beginning, I added the vcxproj files into the .gitignore after some commit and push, does that have any role in my problem?
How can I fix that?

 

[Alhazred]

The answer is: yes, those files are not ignored because already committed before to add them inside the .gitignore

To solve the problem I have used

git rm --cached <filename>

on them and now they have not to be committed anymore when modified.