I take it you mean the 24 MS Office.
Clearing out an old installation generally is little more than using the File Explorer to find the MSOffice folder and removing its contents entirely.
Registry keys in MSO are usually benign and pose little worry.
I would however offer the use of a superb uninstallation program called "Geek Uninstaller" its free or there is a paid version (one time payment) for a few additional non vital utility extras.
Google Geek Uninstaller and get the free version. Run it as Administrator, this gives legacy access to the program and makes it more efficient.
Look in to list of files and right click on each that has "Microsoft Office" as part of its title. There may be more than one. After the uninstaller has cleared the files you will be asked if you wish to Keep the registry Keys found in the uninstaller routine, if you do click Cancel, if not (Best option), then click on Finish and the keys will all be removed.
The Computer whould now be able to install the MS Office with no issues. These are generally corrupted left overs.
Let us or ME know if it works using a PM.
