FANTASTIC! IT WORKED! (Not sure which was the cure; the restore or the running cmd prompt from installation dvd but one or both worked) So thankyou all especially 'Trouble'.........
The problem is that I'm locked out of the admin account and all local users have been removed from the administrators group (a big mistake I know) so running anything 'as admin' doesn't actually run as admin instead as the currently logged in user.......
Hello windows7forums community, I've made a bit of a whoopsey in lusrmgr.msc and have managed to set the password for the hidden admin account; which is fine - the problem is that I also removed the only local user's membership of the administrators group forgetting to check that I had enabled...