Vanished Office

[silverback]

PREVIEW : This problem is now solved, but I'd like any lounge brain power that can sort out what's happened. In the end, I got the friend to buy an Office 365 subscription.
My friend's computer uses Windows 8 and Office 2007; OK, so this isn't a good combination, eh?
His claim (completely unverified) is that 2 days ago everything was working fine. Today, he goes to open an Excel file (which opened OK 2 days ago) and nothing. One swirl of the 'wait a minute' logo and then nothing. Word behaves the same.
Eventually I admit defeat and say I can't solve this over the phone, so I go round.
After a while I establish that Office 2007 no longer exists; it has disappeared from the machine BUT Office 365 is now on the machine. Friend swears he did nothing to install this and he most definitely does not pay a subscription.
How did 365 get there and what happened to Office 2007?
Silverback

[HansV]

It's impossible to know, but I wouldn't be surprised if Microsoft displayed a popup window saying something like "It's time to upgrade your Office" or "Would you like to try out the new Office?", and your friend clicked OK without really reading the message.