Rhino 6.4 requires Win 7 Service Pack 2

Reason why you have to reinstall the KB: Microsoft stops pushing buggy Windows 7 patch KB 4088875

Microsoft no longer installs the Windows 7 March Monthly Rollup automatically, but KB 4088875 is still available in the Update Catalog.

Well aren’t you happy that you got it in time.
I hope this patch isn’t what is required to run rhino 6.4.
/erik