I'm afraid I ignored all of your advice and took the wimpish option of ordering a new Dell Dimension 8300 system - a much more expensive option! Hopefully it arrives over the next couple of days.
Now what to do with my redundant older (700MHz and 15 Gb) system. I thought I might give it to my godson (aged 10) who can surf the net and play games on it.
However, I want to give him a clean machine, with all my files deleted and just Windows XP loaded. How can I do this properly? I was thinking of copying to CD all my personal files (which I want to transfer to the new PC), deleting all the programs and XP and just reload XP. Is this the way to create an "as new" system?