Jon Godfrey works for Technical Asset Management, a company that refurbishes computer equipment for business clients. "The data that their business used to rely on still resides on those obsolete systems," says Godfrey.
According to CBS News Computer Consultant Larry Magid, clearing a computer's hard drive is not as easy as it may seem. "Just erasing the files is not enough. To obliterate the memory you need to use a special program or get professional assistance."
And while clearing computer memory is easy enough with a little effort and expertise, it's not often done. That is a big mistake, according to computer security expert Neil Barrett. "You've basically written out an invitation for a hacker to come and play inside your network," says Barrett.
A London bank just learned that the hard way, when one of its computers headed for resale was bought by a British newspaper and Barrett was asked to examine it.
"Ive got some personal names here," said Barrett as he looked over the computer's memory. He found it held eight years of account details for a string of charitie as well as over 100 files that mention former Beatle Paul McCartney.
Beyond the embarrassment, data left behind on any used computer is a hazard. "Once I've got your digital identity, I've got you," says Barrett.
Britain has new laws to safeguard data privacy - stricter than laws in America. Even so, the booming market in used computers is mostly unregulated in both places.
"The secondhand computer marketplace in Europe and in the US makes secondhand car salesmen look positively respectable," says Godfrey.
In other words, seller beware. More than a just a machine is changing hands; secrets locked inside it could also be part of the deal.