I answered another one on this. I do have the S251i I think (a little scratched).
3 screws. 2 of them are obvious, and under the lid you open to change the bag - they are black ones. The third is centered between the two silver/zinc screws that hold the power and rewind button. You should be able to get to it with a longer screw driver and a flashlight. The lid has to be closed to get access.
Big Smirk, June 2008
