In Windows 7 Netbeans after install as default folder for new Projects use path: c:\Users\[username]\Documents\NetBeansProjects.
Sometimes better way is to make your own path to projects (e.g. on other drive or partition).In order to do this, you have to find and open in text editor projectui.properties file. For Windows 7 it was under c:\Users\[username]\AppData\Roaming\NetBeans\8.1\config\Preferences\org\netbeans\modules. The variable projectsFolder contains path that should be changed.