Dells have something similar. The GXP240 here has a plastic green encasing over the HS, and a the case fan mounted on the back pulls air across the motherboard NorthBride HS, and then over the CPU heatsink fins, and out the back of the case. This is the only fan on the case at all, that's why you can't tell if it's running or not.
Very quiet which is nice in the office. You will probably just have to experiment to see if blowing or sucking the air over the HS would cool the best. If it's an AMD cpu be careful, as it doesn't take much to get them hot.
Just monitor your temps carefully, I'm sure it can be done.
