I sometimes re-use an old hard drives, sound card, video card, DVD/CD Burner, Power supply, and other parts to add to a new computer I bought. But, usually the RAM does not work on my new computer since the RAM on my old computer is very old.
I also usually re-use the accessories like montitors, speakers, USB devices like Printers, keyboard, mouse, microphones, and webcam on a new computer to save money.
I didn't re-use any parts for my current desktop, but I have recycled parts in the past. In high school I would do computer repair for friends and family. I ended up collecting a few cases worth of mis-matched parts. For my little brother's birthday I put together his first computer from those parts and made sure it ran. It was slow by today's standards, but it lasted him forever.
