Because I have a vast number of documents in my PC, each one has its address written in using a macro called prax(). I also frequently add dates to documents.

I don't know, now, what I did but on the ribbon the option INSERT > Date and Time went missing. The "Insert" was there but not the date and time option.

Following Charles Kenyon's suggestion I went to my templates which are at

C:\Documents and settings\(My Name)\Application data\Microsoft\templates

and I renamed the existing Normal templates as NormalOld. I did not rub these out because I needed to recover the macro prax().

I then went to a folder and created a new document. This has the effect of creating a new Normal file which, by the way, has the Insert > date and time option there.

Finally by opening NormalOld I could go Developer > Macros and copy the macro prax and paste it into my new Normal.

( I still don't know what I did to lose the Insert > Date and Time but what the hell ? It is all good again )