And it is sitting right on your desk.

It is your aging personal computer, a piece of equipment that is a lot easier to buy than to dispose of properly. With the rate of obsolescence accelerating - most organizations now consider a personal computer outdated in three years - dealing with old equipment is no small matter. Last year, more than 63 million computers in the United States were replaced by faster, better and most likely cheaper systems. Where does it all go?

Businesses in the United States are just beginning to address that question with some planning and coordination. Those that have taken control of their electronic waste problems are finding it can pay off in many ways.

For Kaiser Permanente, a well-thought-out electronic waste plan has given the company great leverage in negotiating with equipment vendors, said Lynn Garske, Kaiser's environmental stewardship manager. Today, it buys only from manufacturers that meet its guidelines for reducing the use of certain toxic substances like mercury, a requirement that extends beyond computers to medical supplies and even carpeting. (Mercury and cadmium are still used, in some cases, in the printed circuit boards that are found in PC's.)

"We wanted to send them a signal that we were taking seriously the elimination of toxic chemicals," Ms. Garske said. Computer manufacturers have been working for years on reducing the amount of waste their systems create. Apple Computer uses no mercury or cadmium, and has reduced the amount of lead by converting from screens with cathode-ray tubes, which have lead, to liquid-crystal displays.

Michael Green, executive director of the Center for Environmental Health, said that more and more companies were discovering the influence they have on the materials that manufacturers use in making computers. "If a company that buys 25,000 computers says they'll only buy from them if they'll agree to take it back when they're done with it, it can make a profound difference," Mr. Green said.

Like many companies, Kaiser works with a single recycling broker to deal with its hazardous waste, a process it started in 1999. Since then, the company, based in Oakland, Calif., has replaced 64,000 computers. Of those, 10,000 were moved to other areas within Kaiser, and 14,000 were recycled. The remaining 40,000 were sold to individuals and organizations, many overseas, where demand is high for used equipment.

For businesses, the challenge is finding a recycling broker who can ensure that the computers are actually being recycled. While reports from regulatory agencies vary, some estimate that as much as 80 percent of old computer equipment and other electronics collected for recycling end up in landfills in developing countries in Asia, South America or Africa. While dumping electronic waste is illegal in the United States, the international market is largely unregulated, making abuse rampant. To make matters worse, some of this equipment arrives at the landfills still containing private information, including financial and health records.

To try to regulate the recycling industry, the Basel Action Network, an environmental advocacy organization in Seattle, and the Silicon Valley Toxics Coalition have developed rigorous criteria for dismantling and recycling electronic waste. Recyclers that are part of this program must agree to prevent hazardous waste from going to landfills or to developing countries, and they must agree not to use prison labor to take computers apart, once a common practice among recyclers. Recyclers who comply can then market themselves with something akin to a seal of approval. Dozens of recycling companies nationwide have made the list, which is available at the advocacy groups' Web sites, among other places.

Kaiser signed with its recycling broker after weeding out organizations that did not meet those criteria. Most important, Kaiser demanded a guarantee that the data on its discarded systems remain confidential, Ms. Garske said.

Several states have recently passed laws mandating who pays for the recycling of electronics. California requires customers to pay an electronic waste recycling fee at the time of sale. Maine, Maryland and most recently Washington, on the other hand, place the burden on the manufacturer to recycle used electronics, including collecting and transporting it.

Tom Delia, president of Advanced Recycling Technology, a recycler in Hudson, N.Y., said that companies could increase the value of their outdated equipment by taking careful inventory. That way, when the recycling truck arrives the company can easily see which machines are most likely to be resalable and which are destined for the dismantlers. For example, documenting the types of microprocessors inside a system lets a recycler quickly determine its resale value.

"Most companies don't want to put the time into qualifying their technology," Mr. Delia said. For those organizations that keep records of their equipment, recycling is cheaper because the recycler's costs go down, he said.

Mr. Delia estimated that 60 percent of the discarded computer equipment his company receives can be refurbished and resold. "The export market is growing for refurbished computers," he said.

The remainder is recycled, with the plastic, metal, glass and other material separated and sold to various industries. Some businesses and consumers are taking the easy way out by not doing anything at all, Mr. Delia said. He estimates that 1 in 10 old computers is sitting in a garage or storeroom awaiting a decision that often takes an owner several years to make. For many companies, the problem is protecting confidential information. "People are really concerned about their data, so they tend to sit on their old stuff," Mr. Delia said.

That means that individuals and companies often hold on to obsolete equipment until it is too old to be valuable to another user, Mr. Delia said. "The sooner you're done with it, get it out," he said. "The asset value goes down every month."