fluffymark | More geeky help needed for Catt's computer

Windows 98 is being silly. It refuses to install on the basis that it can find an already installed version of itself - although the already installed version is corrupted and fails to work at all. It doesn't give me the option to continue on with the install, it just quits when it finds itself already there. I don't want to delete things, as catt will lose vital files she needs to keep. I've tried renaming the windows folder and COMMAND.COM to other names in the hope it cannot find them, but it still does.

So, how do I fool Windows into thinking it doesn't exist, without actually deleting it?

(or should I just give up and persuade Catt that Linux is the way forward...)