I found that installing zone alarm (Free version) from a bridging CD (From my laptop running ME)prevented WinXP from staying in standby. The machine would reboot after ten/fifteen minutes.
Reinstalling direct from a download seems to have cured the problem.
However 'Webferret' from the bridging disk actually brought up a warning that my keyboard driver was preventing the machine from entering standby. Pratting about with that cost me greatly as I managed to press 'OK' on installing a usb keyboard driver accidentally (Mines Ps2). That lost me control of the keyboard and the mouse. Luckily the recovery disk took me back to factory settings, but I lost some data that was awaiting backup.
Apart from the clock problem, which PC world seem to think is the motherboard, (new one on order) my new arrival seems to be OK.
I do think that Microshaft want their arses blowtorched for releasing WinXP so soon before any manufactures have had time to build drivers for it. I have had to throw out a perfectly good AGFA 1212P scanner as AGFA have given up trying to write a driver for XP. Installing the old one cost me a BSOD the first night of ownership. A warning on their website would have warned me, but nothing there at all to say that their older machines will crash your XP installation. A phone call to their TS dept. confirmed the case.