My Arduino was working fine and i was working my way through 'Programming Arduino' by Simon Monk, i got to section 6 then all of a sudden my programs wont upload anymore....? I dont think its the usb port on the computer, the computer is only 6 months old. Any ideas.....avrdude: stk500_recv(): programmer is not responding.... 
For some reason my board type had changed........ Totally strange. Anyway, thanks for the zero support genious's 