Urgent! Problems installing microsoft office after numerous attempts

Really looking for some help and it's quite urgent as my thesis is due next week!!
I downloaded the free version for a 30 day trial a good while ago and that has since run out. I was using openoffice.org for a while until i was able to buy office.
I bought office today and tried to download using the cd. It told me to uninstall the trial edition which I do and removed it from trash. Started downloading, all fine and was told it was complete. tried opening word but it said it didn't install correctly and i had to uninstall it again.
Uninstalled, removed from trash, restarted computer and tried installing again. Once again, i tried opening word and get the same message! I'm also told that i need to download a 12.2.6 update - would that fix the problem? Although i did download the update the first time thinking this and it still didn't work.

I would really appreciate and help or advice as I am at a loss and am a bit under pressure. I am still using openoffice to try and continue working on the thesis but need Word to fix the layout, references etc etc.

Thank you

No I did that and it removed microsoft office and left it in trash which i emptied.
Turns out you need to do more than just use the remove microsoft programme they provide - there are some more documents and settings that need to be removed too.

Ended up finding a guide on how to do it so all is good! thank you for the reply!