Question: How to remove projects from qt creator, I can delete files from project view but I cant delete my .pro file and my main project folder.

Answer: 
It's a littel dirty way, but go (on windows) into the `AppData\Roaming\QtCreator.ini` file and in `[ProjectExplorer]` remove the projects from:

* `RecentProjects\FileNames`
* `RecentProjects\DisplayNames`

On restarting QtCreator only your needed projects will displayed. 

For Linux, edit `~/.config/QtProject/QtCreator.ini`
As time has passed, it would be helpful only for the future generations, but still:

**If you're deleting subprojects,**
you can delete .pro files of the subproject manually even without exiting the QtCreator: delete the project folder, then remove the line from the main .pro file where your subprojects are listed, then run qmake.

**If you're deleting the main project,**
(if you want to delete the main .pro file from the project itself), it's a little bit unusial, you won't be able to build the project, but if you still need it, Andreas' way will do.