If you are decent with drill and a fine toothed saw, (Hacksaw, recipricating, etc.) then you can cut out holes in you side panel and/or top of your case if there is room.
You can use a CD a template. They are 120mm in diameter.
Use the drill to cut a hole large enough for the saw to fit into and then cut out the circle. Clean off the edges with a file and sandpaper. Put the fan over the 120mm hole so you can mark the screw holes. Drill the screw holes. Attach the fan. Plug it in. Bingo. A case with one or multiple 120mm fans.
<A HREF="http://www.millionmanlan.com/MMLDefault.asp" target="_new">Million Man LAN 2 is June 25-29, 2003 in Louisville Kentucky... Be there!</A>