Some of us just hang on to it, or pass it on as hand-me-downs to friends or family. And some of us donate our old tech gadgets and computers to charity.

But the hard truth is that your old clunker of a computer may be more of a burden than a blessing to many charities.

"I've tried to give the equipment to the Salvation Army -- they don't take it anymore," one man told "20/20."

The reality is much of the stuff ends up in the garbage.

E-Waste Is Hazardous Waste

But there's a dirty little secret piling up with those electronics thrown into the garbage. This "e-waste" is tainted with hazardous contaminants.

The average computer monitor contains more than five pounds of lead. Computers can also contain mercury and cadmium. When you multiply that by the millions of outdated computers and monitors, you've got lots of toxins that you don't want to put back into the earth.

It's environmentally unsafe for individuals to just throw out computers and monitors, but federal law prohibits businesses from doing it.

Businesses usually pay electronic recyclers to haul away the old equipment and pull it apart, and if it's done right, pretty much everything can be reused.

Unfortunately, it's not always done right. That's dirty little secret No. 2: Some recyclers may not be recycling everything. Actually, some experts say most recyclers aren't recycling everything.

"Eighty percent of all the scrap electronics in the United States end up offshore and usually in Third World countries," said Bob Glavin of Chicago, who runs one of the biggest recycling plants in the country.

"I honestly believe there's a secret brotherhood that ships this stuff over there late at night when no one's watching, because none of our competitors do it, but it's all over there," he said.

Waste Dumped Abroad Is Rarely Recyclable or Reusable

Glavin and his son used to export some of their scrap to China, until they went there and saw for themselves what happened to it.

"There was no environmental regulations. There's no safety regulations. There's no data security, because it's not being recycled over there. It's being dumped over there," he said.

"We don't send our trash to China. Why should we send the electronic trash to China?" his son, Jim added.

Jim Puckett, coordinator of a group called Basel Action Network, which monitors exports of hazardous waste, also saw what was happening in China firsthand. Three years ago he documented it in a video called "Exporting Harm."

"What we witnessed was these former farmers cooking circuit boards over little wok-type operations over little coal fires and melting the chips so they could pull them off. These chips would then go to acid strippers using very dangerous acids, dumping all the waste from the process into the river, and that acid process was to extract the tiny bit of gold that was in those chips. It was quite a cyber-age nightmare," he said.

Much of this stuff came from the United States, yet U.S. authorities did nothing. Frustrated, Puckett's group released a second report this past year, this time from Nigeria, where they found the same thing.

"Everywhere there's space -- empty lots, swampy areas -- they'll throw the cathode-ray tubes, the computer carcasses, the plastic housings and routinely set them ablaze," Puckett said.

Puckett says his group saw dusty warehouses piled high with computers and components exported from the United States and Europe, supposedly bought for Nigerians to fix and use.

According to Puckett, however, "About 75 percent of what they were receiving was not repairable, not usable and was simply dumped and burned in the landfills of Africa."

That's what's happening to many of the old computers we get rid of. They're sent overseas. We're simply exporting a huge environmental problem.

"The recyclers that are shipping over there certainly know what's going on, and it's good business," said Lauren Roman, an electronics recycler and an expert on the hazardous chemicals found in household electronics.

Still, some recycling brokers "20/20" talked to insisted that sending the machines abroad helped get computers into the hands of societies that need them.

Roman disagrees with that. She said lots of companies should call themselves waste exporters instead of recyclers. And she showed "20/20" just how easy it is to pass yourself off as a responsible recycler.

You can simply print out a certificate declaring yourself an Environmental Protection Agency-certified recycler.

It's that simple, according to Roman, "because there's no such thing, but you can claim it because most of the recyclers out there are."

Personal Data Often Remains on Discarded Computers

And there's one more thing you should worry about when you throw out your old computer. Call it dirty little secret No. 3. And this one affects you very personally.

Everything that's been on your computer's hard drive -- unless you know how to wipe it clean -- is still there. And it will be there if you donate it to charity, or give it to a friend, or throw it out or recycle it.

When Puckett's group was in Nigeria, they bought hard drives that they discovered had a wealth of private information on them.

"One of these hard drives had documents from the Wisconsin Department of Health and Family services, another from the World Bank. So even if you are not concerned about the environment, you should be concerned about your very, very private data," he said.

But there are some solutions to the mounting e-waste problem. Let's start with hard drives. One good way to trash your hard drive is literally to trash your hard drive. Smash it by taking a hammer to it.

There are also less barbaric ways, especially if you want someone else to be able to use it. There are programs you can buy or download that will truly get rid of everything.

The growing recycling problem is a bit more complicated. Roman and other advocates say we should do with computers and television monitors and fax machines what we do with soda pop bottles or cans: Pay a fee up front that is returnable to you when you get rid of your electronics properly.

Roman says Europe is far ahead of the United States in this regard. Indeed, in Europe it is the manufacturers who are responsible for taking back and properly recycling old computers.

Here's the bottom line: Now that you know you can't -- or at least you shouldn't -- ignore this problem, don't throw out your computers. Look into participating in -- or starting a community-based electronics recycling drive.