the computers might be dead, but individual components are still good.
A tinkerer can put together a Frankenstein machine.
main causes are motherboard failure (over time heating and cooling will cause failure in circuits/solders, impact or static discharge/power surge). If its an older machine its not always easy to get a new motherboard that is compatible with the components.
power supply - desktops but easy fix
RAM failure - reasonably easy
Hard drive failure - easy fix but lose all your data
Don't need a black box, it is just trial and error to work it out.
Depending on the machine and its age, its often more cost effective to just get a new one once you consider parts and labour.
Work IT aren't really interested, the machines are throw away. The most valuable thing is usually the data and it should be backed up on a server.
