I came up against a troubling scenario when purchasing computer and audio equipment on the Internet. I ordered a Sony LCD projector from a supposedly reputable online vendor. But then I called Sony and found out that the vendor was not an authorized dealer. The Sony rep said that if I bought from that vendor, my warranty would be void. So I canceled my order. How can consumers make sure that their purchases are covered by the manufacturer's warranty?

John McCracken, New York

On Your Side responds: I contacted Sony to inquire about its warranty policy. According to company spokesperson Greg Dvorken, Sony provides warranty service on all of its products as long as users have proof of purchase in the form of a bill of sale or invoice certifying that the product is within the warranty period.

If, however, the factory-applied serial number has been altered or removed from the product (which Sony says some unscrupulous unauthorized dealers do), then the warranty is invalid.

Sony recommends purchasing from an authorized dealer because the company requires that such dealers meet certain standards, including informing you of the status of your order by e-mail within 12 hours and offering convenient return policies. Go to www.sel.sony.com for more information and a complete list of Sony's authorized resellers.

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