Hi,
I just started computer repair business. Can anyone suggest a good site for free and paid classified ad? I have visited some links but got no response. Any advice will be helpful.

Craigslist.org is a great place for free and low cost advertising. You could try there to begin with ... you could also start a free blog at bloggers.com or wordpress.com

Talk about problems you run across and folks are searching for offer basic quick fixes they can do at home. But if those don't fix the problem advise them they have bigger problem and direct them to your website for detailed phone consultation (charge them through paypal or other pay service) or have them bring the machine in ...

If you are on a shoestring budget and need to find cheap advertising on the internet there is nothing cheaper than FREE classifieds and they are literally everywhere you can find. You may try a good source like Classified Ad Submission Internet advertisement is essential today to popularize new business and results will be forthcoming.
Best of luck.