First of all 8.1 is not a supported version yet so you can expect these kind of problems. There is no way to create a registry entries if they are blown away by the upgrade so you will have to re-install oracle BUT you can create the database services. Did you read the link I mentioned in the previous post?
mea culpa! I hadn't realised it was a link
Yes - that worked perfectly.
Not sure what's happened with the registry - as part of my attempts I'd copied registry entries from my desktop PC (Winows 7) to the laptop - the one with 8.1
Used the oradim command, and netca as described in the link and now I'm back in business
Thanks you so much.
I knew Microsoft and Oracle weren't exactly the best of friends, but deleting Oracle is a bit over the top!