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#91
You can System Restore to before you deleted the Registry Key, even before you uninstalled Norton. Then uninstall Norton in Control Panel, followed by running it's uninstall tool.
Show all System Restore points to see if you still might have one before you installed Norton in the first place. This would be as if it was never installed in the first place.
Did you read in Clean Reinstall - Factory OEM Windows 7 the tools recommended which guarantee perfect Win7 performance? There is even a link to Microsoft Security Essentials. The reason I ask is that you say you followed all of those steps.