This article on this BBC isn't the first one I've seen warning about disposing of your old IT equipment securely, but it raises the issue again, and it's an issue a lot of people seem to be unaware of. Everybody seems to have been scared by the constant reports of viruses, tojans and hackers stealing you bank details, passwords and everything else from you computer. Firewalls, anti-virus and spyware removal tools have become essential tools in the new always-on internet age.
Some people are unaware of the other risks associated with PCs, which often store many of your most personal details. Add to this the fact that we're all being encouraged to recycle our PCs (and rightly so), which often go to third world countries. The risk comes from your hard disk drive (HDD), which is where all your data is stored. You see, simply deleting documents or formatting the drive isn't enough to hide the data or remove. The only way to securely remove your data is to overwrite it with junk data. The US Department of Defense (DoD) and the Royal Canadian Mounted Police (RCMP) standards recommend three sweeps, but it's been suggested this is too low, supposedly the DoD has a higher level which demands seven sweeps, which takes a lot of time for a big HDD, and Peter Gutmann's method involves 35 passes. One or two sweeps will probably suffice for most people, three at the most.
To do this you'll need a specialist piece of software (unless you have an Apple, which includes the software on your install disk), something like Darik's Boot and Nuke (free, any computer), Eraser (free, Windows only), SDelete (free, Windows only), others recommendations can be found here.
Something else to think about is storing your details in an encrypted format on your computer. You can encrypt your entire HDD, but it slows the operation of the machine a lot, you can find utilities to encrypt files and folders easily though, and make sure you use a password manager to store your passwords encrypted in case someone does get access to it.
If your HDD goes faulty before you clean it (all the solutions above are software and only work on functioning drives) you're faced with two choices: the RCMP recommend shredding drives while the MoD go for acid baths. Just so you know. A hammer, some time and making sure you bin the parts separately will probably do the job.