Installation Trouble PLEASE HELP!

I am trying to install the newest Version of Libre Office on a client computer, and it seems they had a previous version of 3.5 that was uninstalled incorrectly, and the .msi file is missing so I cannot install a new version, or uninstall the application. I cannot find the 3.5 version .msi file on the website, and I tried downloading one from a third party website with no luck. I would really like to get this up and running on this PC without having to completely reformat the drive. Any help would be appreciated as to how to resolve this issue.

Thank you

Any help in this previous Q&A?

In addition to David’s answer you might find this one helpful: Uninstalling LO 4.0.3 in W7 without msi file

Especially old installers archive: Index of /libreoffice/old