My desktop computer just shut down in the middle of working. It is now completely dead; initial investigation showed that the surge protection had died, tried changing the fuse, no good, put the original fuse back in and it started working again, but the computer is still completely dead. Can I assume that the computer's power unit has failed (it is over 5 years old)?
You put the original fuse back in and it started working again? You could assume that the power supply has failed but you might also need to consider that the other parts in your computer could have been damaged along with it.