Thanks I have done that now. However, there seem to be different TTF fonts in the Fonts folder - I suspect I have moved some in which shouldn't be there.
Do you have .TTF and .ttf fonts? If not which? The .TTF ones seem to have an O in the thumbnail rather than TT. I also have All res fonts .FON with an A in the thumbnail. In addition there are some fonts listed which are just shortcuts. The attributes column for each font has has either A RA H or nothing.