I am really confused.....? (UK)?

Right- we own 2 laptops and 1 computer in our family home. And we have had microsoft office 2000, and 2003. But we have had a student/professional 2007 Microsoft- trial for 60 days. And then it ran out last month. So, we got another one exactly the same. But, now it won't really work propily. We put the disk in, and then the product key and all that stuff we fill it all in, and etc...then says it's ok and trial installment was successful etc....and then we open one of them- eg.- Microsoft word. And then it says "Your trial pack has gone out of date and stuff...do you wan't to convert etc..." And then it won't let us use it at all. Also, I have gone onto the control panel on windows start- to uninstall the last one we had and stuff.....what is going on?! I really need it too work! Helllppp! :)