Help! What features should I look for in a computer. What brand is best? tablet?

I am trying to buy a laptop but I do not know what I am even looking for. I know I need something that I can do school work on. I need something fast and I like to burn music. I know nothing about Ram, vista, g's. I tried looking on consumer reports but I need some guidance because I am confused. I have a Dell now and it is pretty good but so slow. I have been looking at the Latitude XT tablet, but I know nothing about it so any advice would be so helpfull. Even just an expalnation of how much G's and Ram and intel's and what type of Vista to look for would be great. Thanks!