Vista - machine died during windows update installation

I cannot believe my luck - shutting down my computer windows vista says it is installing the latest updates (do not switch off power) and then bang, there's a power cut !

Now when I switch the machine on it is trapped in an endless loop of trying to finish the installation, finding a problem so it restarts. I have tried breaking into windows as the machine boots up but nothing seems to stop the looping.
safe mode has the same problem
bringing up system restore only gives me a choice of rolling back the last 2 checkpoints - and neither will complete without an error.

I'm stuck - and would rather avoid attempting to use a restore OS option unless there's no other way.

Any suggestions ?

There is way to stop this loop:METHOD THREE from this link:The update is not installed successfully, you receive a message, and the computer restarts when you try to install an update in Windows Vista

see also helpful link how to edit registry remotely from WinRE (from post 17)
Can't Delete Registry Key

Thanks. I managed to stop the machine looping by following this. A side effect was that Windows update then stopped working properly - but Vista's self diagnosis managed to find me a registry download which ran and corrected the problem.
End result is all is now working fine.

Many thanks

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