I am also running Online Computer Repair business.. But it is Offsite. They
best thing to do is promote your business online. Hire any SEO Expert. Who
will advertise and promote your business online. You have to give him certain
keywords such as " On-site PC Repair Service" "Fix computers On-site" i am
sure SEO expert will assist you in this. I would suggest you to hire any
independent contractor from freelancer.com. It is cost effective and they
offer good services. Before you hire any freelancer for your work. Make sure
that you check their ratings, reviews, past projects, current projects. I am
sure it will help you to get more business for your computer services.

You have to advertise which starts with marketing.  Marketing is about understanding your customer - their needs, their wants and where they find information.  Then, design a message that prompts them to find your business and get the message in the places they are looking. I assume you are a local business - have you looked into trying to get free plublicily like getting your local paper or TV stations to run a piece about your company. Have you tried direct mail or flyers? Are you getting current customers referring your business to their friends and family. Bringing in new customers takes time and effort.  You have to try something - measure its results then either keep it, tweek it or scrap it for something else - That is business!