PC Shuts down when inserting dvd/cd in drive

Hi Folks

Happy new year in advance

How wierd is this? I have been having problems for a while each time I insert a dvd/cd into the drive the PC would shut down and would not reboot unless you unplug the power lead then plug in again. I changed the drive and it was ok for a while so thought I'd solved it. It started happening again so have just swapped around the power leads to all the drives and it seems ok again.
I have a 500w PSU, could it be failing? its been in the pc for a few years just seems odd that just swapping the leads seems to have (for the time being) cured the problem.

Thanks in advance as always for any and all help given.

It sounds like your power supply is tripping out from what you describe. After that happens, the unplugging from the mains is what you need to do to reset them. It could be a faulty power supply, but it could also be damaged cable insulation causing a short circuit, or a faulty component causing an overload - I would have said the drive is the obvious candidate if you hadn't already changed it. Carefully inspect all the cables and see if you can spot any damage.