Don't know if it's the same for your model, but I just figured out how to open model U4655. I found it easier to separate the upright part from the base first. Also, pry off the knob for the height adjustment slide.
On the bottom, just behind the brush roller there are two slots, one on the left, one on the right, near the edge of the base. Put a large flat screwdriver into one slot and give it a twist. Repeat on the other side. Now you can remove the piece that covers the brush roller, and the brush roller, if the old belt is broken.
The base and top cover just snap together. There are no screws. Just start near one of the rear wheels and use the screwdriver to push the cover away from the base, and work your way around the base. That should do it.
David, December 2007
