Still stuck? Remove the 5 screws from underside of the base unit with a cross-head screwdriver. Insert flat blade s/driver through slot in base to hold screw in place and turn the plastic liquidiser drive clockwise (you made need to grip it lightly with pliers to do this). Finally prise off the plastic collar at the base of the mixer drive spindle (it's shaped like an inverted cereal bowl). You can now separate the top from the base and access the drive belt. Tip for fitting belt: warm the new belt in hand-hot water for a few minutes; this will soften it slightly and make it easier to fit.
Good luck!
Richard Philpott, January 2009