I had the same problem a few months back managed to get it sorted. I googled this several times and mostly people had posted product keys but none of these worked as they'd been used previously. What i did find was that if you click 'cancel' when starting the office programme, and therefore never starting the trial period, bizarrely you can still use the programme in its entirety and as the trial never started it never runs out, very weird. Obviously in your case this is too late so another option i found was that someone had posted an answer to get round your problem. That is by changing the programming code in a couple of the registry files you seem to be able to use the product no problem at all and it's worked for me ever since. I can't remember exactly which site it was but searching something like 'microsoft office registry code hack' and you'll find it. It only requires a little know how and was pretty easy to do. In fact just did the search for you and the site i used was
http://www.mydigitall...uation-trial-version/
I hope this helps.