Thanks for the advice. I'm pretty certain it was the
PSU. I took a working
PSU out of an old machine I'm keeping for spares, connected it to just the mainboard (including graphics card), fan, hard drive and wireless adapter, and the machine booted up with no problem. I then reconnected the old
PSU to check, and the problem re-appeared - so pretty clear evidence.
I'll get a new
PSU, but how big a
PSU do I need? The faulty one was 400w, and the new one I'm using temporarily is only 300w, so is not going to be sufficient (so I've not reconnected all my optical drives etc to save power). When all is reconnected, the spec. will be:
Gigagbyte KT400 mainboard
Athlon XP2600
CPU
1 Gb
Ram (2 x 512)
Maxtor 80Gb hard drive
Hercules prophet 9600 series 128Mb AGP graphics card
CD-RW
DVD-RW
floppy
internal Zip drive
USB optical mouse
USB wireless .11g adapter
All other USB devices have their own power supply (scanner, printer)
Thanks for the help