Yes you are in the right area. But a bit more info would be of help.
I'll start on the understanding that you are attempting to get new customers from existing small business who do not have a dedicated IT support team in house.
The best thing you can do is tell them what type of service you offer and what your aims are as well as your response times. Also what type of OS you cover and what it is you actually do.
NEVER e-mail these to any company but send them by post as that way they just might get filled and then pulled out when they have a problem. I'd also advise enclosing a business card as that should get kept.
Unless you have at least one satisfied customer you Will be up against it as the best form of advertising in this area of the IT business is still word of mouth but at least you can try sending out what would effectively be nothing more than a CV and somewhere here on TR they have a "White Paper" on Outside Consultants that you can alter to suit your needs and then use it as a Confidentiality Agreement between yourself and the Company.
The more professional your letters look the more they are likely to be filled and not end up in the rubbish bin. Begin by concentrating on the small business and send them a complete Over Vier of what you are offering along with a copy of the Confidentiality agreement even if it is nothing more than a basic form type page that can be altered as required, it wouldn't hurt to have this on the bottom of the Confidentially Agreement or maybe something like "Sample Only."
You would also have to put on record your charges and weather you prefer a pay as you go arraignment or a Monthly retainer where you will be at their service as a first option rather than the pay as required clients.
That would be a good starting point but If I've made the wrong assumptions from the beginning then none of the above applies.
Col