I know this is a silly question but... Iv seen Pentium D's with speeds of over 3Ghz, but the highest core 2 duo speed is 2.93Ghz - so why is the core 2 duo stuff regarded as better?
Because it actually is better. A core 2 can do more work with fewer cycles than a pentium d. I wont go into the details because you can find them all over. This article is a good one http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2795