Before you start looking at keywords, you need to fix your goal firmly in your mind. There are basically two major reasons to do SEO.
This may come as a surprise but there are people out there who don't know that you exist. SEO is a powerful and inexpensive way to get your name out there and build some credibility with your target customers. There are three major types of brand awareness:
Company brand awareness works on getting the name of your company into the market. If you want to build credibility for Big Computers Unlimited as a whole, then you probably want a campaign focused on getting your company listed where other top producers of PCs are listed. PC, computer, or fast computer all might be good terms.
