You might also donate it to a local church or school or nonprofit. In any event, you face an issue when disposing of your old computer that others don t. You need to be sure it contains no client secrets or confidences. If you have storage space enough, you might want to not get rid of the old computer at all. It might not meet what you now think of as your new level of needs but in an emergency that takes out the new computer, you might suddenly find it very useful to be able to pull out the old one, dust it off, and get something done.
Parts are often useful for similar reasons.
The old keyboard may not be as comfortable as the new one for everyday use. But having it around when the new one has a cup of coffee or a glass of soft drink spilled on it could be a godsend. Being able to pull an old unused drive off a shelf and put it temporarily in her computer so as to install the driver was extremely useful. There s no point in keeping a 2400 and a 9600 modem in addition to the 28,8 modem when you upgrade to the 56K one. But a law office that has room for multiple Bates stamps and some old corporate seal presses not used in years can find room for other old, but not broken, equipment.