I normally use VS 2019 and VC 7, but did some experiments with VC for Eclipse and VC 8 last autumn. Since these experiments didn't turn out the way I had expected I uninstalled VC 8, but when trying to open VC 7 that didn't work at all. I tried first to repair and then uninstall VC 7, but neither worked. I'm afraid I have created a real mess of this so the best thing would maybe be to manually delete all crucial points in Windows Explorer and the Register Editor. Is that possible and what should I do in that case?

What is the error that you receive when you try to Repair or Uninstall Visual COBOL 7?

When all else fails you can try using this tool:

Fix problems that block programs from being installed or removed - Microsoft Support

1) If I click on "Micro Focus Visual COBOL for Visual Studio 2019" in Control Panel - Programs and features and then choose Uninstall/Change a window will pop up for a split second and then close again. 2) If I try to reinstall VC for VS 2019 the same thing happens. 3) If I try to install the latest Patch Update the same thing happens. 4) I ran the Microsoft Support tool in the link above, but unfortunately VC for VS 2019 wasn't listed among the apps that could be uninstalled. 5) During my attempts yesterday I tried to "uninstall" by removing some MF folders in Program Files and some keys in the Registry. That was obviously stupid ...

I am not sure this will help but you might try what's in the following article. It is for Enterprise Developer but applies to Visual COBOL as well.

Installing EDVS2019_70.exe, a blank window pops up and then disappears. (microfocus.com)