Problems closing Rstudio


I had installed R 3.4.4 almost 5 weeks ago with Rstudio. My system crashed for some reason, and then I could not see the icon from RStudio on my desktop. It seemed there was not installed at all. I decided to uninstall R 3.4.4, and install R 3.5.0. However, the control panel did not show R 3.4.4 neither Rstudio as installed software.

Then, I decided to install R 3.5.0 and RStudio 1.1.447, but I was having the same problem. Rstudio 1.1.447 was working fine, but suddenly it was not "quitting" right away. It took a long time to close the editor. Next time when I turned on my computer, the operating system found errors, and began repairing those errors. Finally, windows 7 starter showed, but Rstudio and R 3.5 were not installed anymore. They did not appear in the control panel as installed software. The software files remained in their own directories, but there were not *.exe anymore. I was looking for an Uninstall tool, so I can uninstall previous versions completely. I did not find the *.exe file as stated on the readme file.

I deleted the sub directories from previous versions, but I am concerned about the registry keys and the updates on the system files the software handles.
Now, R 3.5 and Rstudio (latest version) are working fine, but I would like to know how to uninstall completely the previous versions.
I am using Norton Security software. I do not know if it has relation with the problem I had.