For the 2nd part:
To set OpenOffice Writer as the default, right-click on a .RTF file, click Properties.
Click "Change"
In the Open with dialog, click "More Apps" and scroll down to the bottom of the dialog.
Click "Look for another app on this PC"
Browse to locate this file
"C:\Program Files (x86)\OpenOffice 4\program\swriter.exe"
OpenOffice Writer will be set as the default handler for .RTF files.