there are hardly any 'fast' single core computers nowadays and intel will end single core production in 2008. vista and photoshop definitely takes advantage of dual cores. and even if the specific program you're using doesn't, most PC's are always running 5-10 programs in the background at any point in time. you don't shutdown email to surf the web, or close your browser to play music do you?
Is it better to buy a really fast computer vs. these 1.6 ghz dual cores? Is Vista or any other program (Photoshop, Nero, etc) out there making using of the dual core?