If you have a previous version of Microsoft Project installed on your computer, the Setup program detects it and asks you if you want to remove it. If you want to keep two versions of Microsoft Project on your computer, type a different folder or directory name indicating where you want to install Microsoft Project. When the Setup program replaces a previous version of Microsoft Project, it replaces only the program files, not your project files.
In Microsoft Project, you can automatically open a project file you created using Microsoft Project 4.1 and 4.0 without any special conversion process.