Thanks for the replies, and indeed the links.
This all came about when this morning I went to start Word 2007 in Vista. It said something for an instant - I think it was about another copy, not sure.
Anyway, it started installing Office again! I stopped it sharpish.
I can only think the installation of Office 2010 in D drive under W7 boot, somehow affected the installation. But I had assumed the boots were totally isolated OS entities.
So, that or coincidental failure. One never ceases to be perplexed.
I think I shall strip the partitions and only use W7. Word 2007 was the only reason I was keeping it on and the key is in London somewhere. Oh, it was nice to boot in Vista to help my UK pal. Imagine me giving advice to a computer user.