Each template exists in the [HKEY_CLASSES_ROOT] hive associated with a file extension. Whether it is visible or not in the New menu is controlled by whether the related entry has a sub-key called 'ShellNew'.
For example on the New menu there is usually an entry for "Text Document". This is visible because of the Key:[HKEY_CLASSES_ROOT\.txt\ShellNew] If you were to rename the key so it no longer had a sub-key called 'ShellNew' by changing it to [HKEY_CLASSES_ROOT\.txt\ShellNewOld] it would disappear from the New menu.
1. Open Regedit, and using the Find function (Ctrl+F) search for any values of 'ShellNew'.
2. Several should be found under the [HKEY_CLASSES_ROOT] hive, if you do not want them to be displayed rename 'ShellNew' to 'ShellNewOld'.
Note: Changes should take place immediately without needing to reboot.
