Ok. I have solved the problem. I have completely given up on Vista and upgraded (and yes, the word is upgraded) to XP. My Dell XPS is now a fabulous, fast and easy to use machine. Can't understand why Dell recommends Vista, their kit is sooo much better without the additional burden. All my software now works again, I've got back 40Gb of disk space (30% of my hard drice capacity). I recommend this solution, if I had done this when I first had the problem I would have saved a week of my life trying to fix the Vista problems. After my initial post in August last year, I put my 'problem' machine aside while I tried to fix it and used an old machine, it finally had a hard disk crash last week, forcing me to do something about the Vista machine. Don't hesitate, just get out your copy of XP and do it!