thanks guys i really appreciate the fastness of your answers...I myself am a long time mac user and have several times upgraded internal hd on PowerBooks and iBooks without problems...but recently i have stumbled upon a couple of discussions on the Apple web site: http://discussions.apple.com/thread.jspa?threadID=2054387&start=1950&tstart=0 this one is 130 pages long!!!!!
And:http://discussions.apple.com/thread.jspa?threadID=2049659&start=1980&tstart=0
which would instill doubts to the most competent of Apple hardware expert...