Heyup mouseboyx - tried pressing each of the function keys on startup and the only screen that loaded was the Boot to Safe Mode +/- networking / directory services etc. So I think will have to wait until I can get hold of my recovery discs until I can try and use the Vaio recovery utility. Thanks for the tip though.
Thanks for the reply Girderman - I will try what you have suggested when I get hold of the recovery discs (they are on the other side of the UK at the minute, so not very far at all). Just to clarify, I don't think I run direct from the Administrator account: I use 2 accounts as mentioned, the limited one for everyday use to protect the system from changes from malware etc. Also whether I'm loading Safe Mode, or Normal Mode the same thing happens: I am still required to click on a user to login as that user - usually there are 2 shown for "normal" logons (Pete and System Protection), but usually in safe mode there are 3 user names to click on (the above-mentioned 2 plus "administrator") - now there are no icons or logon boxes or user names where there used to be, just the logon screen with windows blue and logo in the background. It's almost as if the computer has been setup without any user accounts at all (including admin accounts) to logon to.
Anyway - will post again on what happens when the Vaio recovery programme starts