It's a bit of a drudge, but you'll find quite a few specific suggestions in this discussion at NibbleGuru, where the issue has been reported by numerous people for different versions of Oracle.
http://www.nibbleguru.com/probs/145/7
In general, however, ensure that your Windows updates are all installed, and any updates available for relevent software that is running on your system. The suggestions in the link above seem to point mostly to configuration problems which mean that the database isn't actually running before you try to connect to it.
Beyond that, I'll leave it to someone more specifically knowledgeable than myself.
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Grandad
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