Further to my note of 30/11/06 I set out to do a scannow as suggested by keef66. I had never heard of this and didn't know what to expect. As soon as it had started there was a message to insert the XP CD-ROM. I cancelled because I only have the original Evesham Recovery disc and I was scared stiff that if I put that in, it might reinstall Windows and I'd lose everything! Can someone reassure me that the Recovery disc will do the job?
If your disc has this follow these instructions: click here
sfc won't overwrite or destroy any existing documents, folder, files etc. - it is likely to undo any registry tweaks you may have made, but is probably worth the effort of redoing them (if applicable).