I want to make my home business legitimate, how?

Years ago I started fixing computers for friends and family for dirt cheap just for a little extra income. Since then it has evolved into a fairly busy side-job. I have a constant flow of repairs and satisfied customers. I need to make this legitimate. How do I go about registering my business? How do I get a bank account for my business? Can I get a credit card in the name of my business?

Thank you for your answer = )