ChemBioOffice can't be installed because it already is (but it's not)

I tried to uninstall ChemBioOffice 15 and reinstall it, but after uninstalling the new installation fails because aparently ChemBioOffice is still installed. But I can't find any ChemBioOffice 15 files anywhere on my computer. Maybe I uninstalled it incorrectly, but now I don't have ChemBioOffice but I also can't install it anymore.