What kind of CPU is the best?
Right now, the current new CPUs are from Intel called i3, i5, and i7. I currently have an i5 on my Sony laptop and it's fast.
What kind of computer to get?
Regarding your computer purchase, it really depends on what you want to do on the computer. If you want to get a gaming computer, the best will be the i7.
I would recommend going to a store and looking at the windows review of the computer you are interested in. You can do that by going to the desktop, hit START, right click "MY COMPUTER" and select Properties to view the rating it has against others.
Also, if you are a student, you should look online at the manufacture's website for any student discounts. I received a student discount for my Sony laptop. I basically paid the price of the Sony i3 from Best buy for my Sony i5 CW series.
Company brands info?
In my opinion, I like Sony and Asus. I stay away from HP and Compaq.
Also, I look at customer reviews and reviews on CNET.com on the products to see if it has problems or not.