Computers, like most other electronics, contain harmful chemicals which can be dangerous to the environment if not disposed of properly. Thus, it is very important to safely dispose of your old computers and electronic devices.
Here are instructions:
1. If your computer has valuable data, back it up somewhere. For example, you can use an external hard disk, a pen drive or the hard disk of another computer.
2. Securely delete all the data. Just deleting the files and folders is not sufficient. Even after you delete the files and folders, it is possible to recover them. Deleting files securely is particularly important if you have sensitive information such as credit card numbers, bank account details, passwords etc stored on your computer. You can use a file shredder tool to delete all your data securely.
3. Find a computer recycler locally and give your computer to them. Normally, most computer recyclers will not charge any money from you. However, some do.
Remember that the best way to recycle your computer is to continue using it as long as possible. For example, if your computer has become unusable due to the failure of a particular component, you can have it replaced and continue using your computer. Even though you may not be able to use old computers for day-to-day work today, you can use them as a backup computer or for other purposes.
You can also install a lightweight Linux distribution on your old computer and revive your computer. You can use such computers for surfing the Internet, checking their e-mail, listen to music or lightweight office use.
You can also donate your computers to other people. For example, if you know any kids who could use a computer, you can give it to them. You can also donate your computers to certain charity organizations. There are many organizations which ship used computers from developed countries to developing or underdeveloped countries for use in schools etc.
Last but not the least, you can also use the computer hardware creatively. For example, you can use your computer cabinet for storing books or other items. You can also salvage parts and reuse them in other computers.