i've moded the side of my CoolerMaster Side Panel, and it was really easy if your careful. Heres what you do.
63-68mm Hole Saw with a 1/4 inch drill Mandrel (bout 20 bucks AU)
5/16 inch drill bit (bout 5 bucks AU)
80mm CoolerMaster Neon Blue Fan (my choice)
A stylish 80mm fan grill.
tape the front and rear of your cm stacker window with masking tape.
place the 5/16 drill bit on the drill, and slowly drill the pilot hole for the holesaw.
Replace the 5/16 drill bit with the Holesaw and line up the pilot hole woth the drill, the start drilling really slowly (speed 1 on the drill), eventually the holesaw will push through the perspex.
Now that you have your hole, place the fan over the top of the hole and use a pencil to mark the four holes for the fan. Then grab the 5/16 drill bit and slowly drill the four holes.
Now that all the drilling is finished, clean away the the debre and remove the masking tape.
Screw the fan grill and fan on to the case, make sure it is not to tight or your crack the perspex. Then its all DONE!
I hope this is helpfull
you can MSN me on Saiyan_Trb@hotmail.com if ya want a hand while your cutting the window.