Will ReadyCache have a driver for Windows 10?

Contact support and tell them you need the Beta tool called  Windows 10 cleanup. They will email you the link.

I had the same exact issue and had already deleted  my Windows.old folder. This tool worked for me.

When you run it, the command window flashed the screen for a second, then it is done. You should be able to run the ExpressCache installer with success. 

Kind Regards,

Chris