This is just a post to help out anyone trying to install RStudio to a Windows 8.1 OS. The site instructions state the current RStudio download is for Windows 10/11 because they are 64bit, however the 8.1 OS can also be 64bit.
Check your computer (start menu > system) and see that it is 64 and not 32. If it is you can download the current version and see if it will work for you. It will place RStudio in your apps.
I saw a number of responses recommending you download an earlier version of RStudio, but that's doesn't seem to be necessary if your OS is 64 not 32.