After digging around I managed to find the bits and pieces associated with this laptop. Predictably, the recovery CD is not there. I found the XP and Sony manuals, loads of useless Microsoft Office bull and all the packaging. No recovery CD.
Also predictably, tapping F10 at startup just sent me to a black screen that did nothing for 15 minutes. Sounded like the laptop had just given up, wasn't making a sound and no lights were flashing.
I took a look online to find a recovery CD for the Sony Vaio PCG-631M, but couldn't find anything that looked really helpful.
http://www.user-guides.co.uk/Sony/Recovery/Sony-Vaio-Recovery-CD.htmhas some recovery CDs for sale, but I don't much fancy buying one for a terribly old laptop that I only really want so that I can work outside of the house. Also, doesn't look like my exact model is listed there. [Apologies if this breaks any linking rules].
Thanks again, any more thoughts?