Running a genuine W7 x64 Ultimate on my iMac (bootcamp) and I'm getting Windows Update errors relating to Upgrade to Windows 10 Pro (code 80240020) every time Windows Update checks for updates. FWIW, there are numerous others reporting the same thing on MSFT support forums.
In the Get Windows 10 app, it shows my PC as ready (no errors or incompatibilities for neither hardware nor software) and it just gives me the option to get notified when it's ready.
But I guess it's already downloaded the W10 install files because when I run Disk Cleanup (for system files) there's now an entry there for Temporary windows installation files that's 6GB in size. Maybe MSFT doesn't think it's my turn yet