Still in warranty? also have you ever taken a laptop apart before?
if in warranty send it back to pc world or ask for a rmd.
if warranty is over then take apart the laptop and clean the mouse area checking for broken or loose pieces. if you cant find the source of the problem you should be able to order a mouse replacement through pc world. just unplug the ribbon cable and fit the new mouse then plug the new ribbon cable in. done, easy peasy. cost for full mouse replacement should be around fourty to fifty us dollars. good luck
greg, June 2009