According to a 1999 report by the National Safety Council, 53 million computers are expected to become obsolete; 80 percent will go directly to landfills, some will be recycled and many of the remaining machines will be donated to charities.

However, as the numbers donated to charties increase, so do the headaches since many of these machines are too old, don't work, and have no operating system. Accepting equipment that can't be used simply raises the cost for the organization as they have to find a way to recycle the equipment and still get the hardware and software that's needed to run the organization.
...from Charities Say No to Obsolete Crap in Wired News