I figured it out. You have to peel off all four rubber pads attached to the grill to access the screws that attach the grill to the main body. Unfortunately, that leaves me with the problem of how to reattach the four rubber pads. I have some spray adhesive that might work. Putting the screws under the rubber pads is not the most user-friendly design.
I have a Cooler Master NotePal ErgoStand (model R9-NBS-4UAK). A lot of dust has collected in the grill and on the fan. I don't see any way to open the thing to clean it out. Can anyone tell me if there is a way to open it? I've written to Cooler Master support, but so far I have not yet received a reply. Thanks.