Hi anonymous userDoerner-1014 ,
Welcome to our forum!
As I know, support for Office 2007 ended on October 10, 2017, which means that you'll no longer receive Office 2007 software updates from Microsoft Update or security updates and no further updates to support content will be provided. It's suggested that you could upgrade to a newer version of office for a better user experience.
According to your description, I noticed that you have deleted the Registry entry and fix Outlook program but they didn't work. Since Office 2007 is no longer supported, I can't test in my environment. Through my research on my research, I find a similar thread with yours which mentions that Outlook 2007 works after he uninstall and reinstall office 2007. I notice that you don't want to use this method, but I'm afraid it's a better suggestion to try at present.
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