Windows 8 I installed MS O10 on my PC - Office, Home and Student - Word, Excel, Powerpoint, Outlook. All installed without error. I can open all . . . except Outlook. FWIW, upgrading Outllok from 2007. Every time I clock on the Outlook desktop icon, I get popup asking me to enter my 25 character product Key. I do that, and Office apparently installs the files . . . again. after this, Outlook opens but over that is the Product key popup. I've entered the Office key 4-5 times and I get in the same loop. I tried the Outlook 2007 product key and get "invalid key. How do I get outlook to load?