Thanks for the replies. I've looked at Toshiba's website and they recommend doing a clean install rather than an upgrade for my model of laptop, so I think I might go that route after all. They even supply a utility that, apparently, will re-install any Toshiba code that needs to be done after Win 7 - although I guess that might add a load of rubbish back that I don't need anyway!
My drive is partitioned into several logical drives - if I install onto C I presume the others will be left intact? It doesn't insist on formatting the whole drive?
Oh, and another thing. I currently have a 32-bit version of Vista with 2Gig of memory - is there any point in going to the 64-bit version if I don't expand my memory?