Thankfully this was not the first time I've had to dig into the guts of this machine, having previously changed the CPU and then had to change the motherboard as the original could not handle a 125W CPU, I've installed RAM strips more than once, also EIDE cards including video cards, plus had the power supply unit quit and had to change that, as well as changing the CPU cooling thing for a rather large coolermaster one.
Biggest problem this time was isolating the cause of the failure, help on here especially from
@SpikyMikey, was really helpful. OK, I made a silly mistake or two but all is now well, especially as Firefox synced with my phone so I have all my saved logins back.