simple htaccess question

[mrthumbs]

How do i rewrite everything for

www.domain.com/x/y/f.html
www.domain.com/test.html
www.domain.com/dfdsf/fsdfdsf.html

etc etc

to

www.niamod.com/x/y/f.html
www.niamod.com/test.html
www.niamod.com/dfdsf/fsdfdsf.html

??