Well the new powersupply seems to have done the trick as I am writing this on the resurrected machine. I'm still not 100% happy with it though. When powered down the IDE status LED on the front of the case stays dimly lit, as does the LED on the CDRW. My investigations lead me to believe this to be a fault on the Secondary IDE channel and/or problems with one or both of the CD/DVD drives. The IDE LED is related to the actual IDE cable, where the drive LED seems to be related to the molex power connector. I suspect some damage to the drive from the old power supply or degrading capacitors leaking a little. I am going to monitor the situation, hopefully it will not be an issue and the system will run for another few years.
Getting the system booting was another long haul again, it seems that all the powering off via the front power button whilst testing the hard disks upset the bios. This caused it to revert to a previous backup version, not the best backup version either. The solution was to flash it with a new bios, allowing normal operation to resume.
The new power supply is a Seasonic S12 500W unit, I like it. There are one or two things to think about before putting one in a system. It supports SATA and Molex power connectors,Â 3 molex each on two cables, 2 SATA power on two cables. There are also special power connectors designed for new graphics cards. I was disapointed to find that with the molex connector positioned how they were it was difficult to connect my 4 IDE drives along with my graphics card. My graphics card uses a molex connector, not one of the new connectors, I only have one SATA hard drive. This means I have alot of unused connectors and a couple of cables maxed out. Futureproof wise its an excellent unit however maybe not the ideal choice for an older system. The power supply fan is as good as silent and I have no doubts about the quality of the unit. I'll be buying Seasonic power supplies in the future.
I conclude that Project Zombie has been a success, it could have been a cheaper success if it wasn't for all the new parts but its running again.