Hi there,
I am having the same error code "0x81000005", but on updating Microsoft Office Professional Plus 2010
with Windows 10.
I insert the right Product Key, which is received correctly from the system, I then get asked to install, and get full access.
But the next time I try yo access Office I am asked once again to insert the Product Key: what am I supposed to do?
Many thanks
Michelangelo