Many thanks all for the continued help,
The machine started out with just 64MB, so I bought 256MB extra from Offtek.co.uk.
It has been fine, and was recognised as working as recently as the older day on one of my countless Win ME re-installs. My feeling is that the chip is still perfectly serviceable since I have been very careful in its handling.
I just removed it for the clean new install of XP which so far has gone perfectly - happy just to have some feeling of confidence coming back....but it would be nice to get some speed back into the machine (which was why I expanded the memory).
At the moment, with the extra 256MB plugged in, the power up screen just doesn't appear. I just hear a whirl of a fan, then nothing. I have to close the power button for 5sec to force it to shut down.....Remove the extra, and it powers up with no problems.
I know I have to update the modem and video drivers anyway (for XP - as I remember doing this before) and all the hotkey functionality....but I think it might be the BIOS....
I have been to the SONY VAIO website, and there are downloads to adjust the BIOS for my particular model to suit Win XP.
I think I shall start with those. I'll let you know how it goes.
LF
PS: Paco - does this sound correct? I mean the BIOS causing the upset? Thanks for taking the time.