Who can help me register my Word?

Hi. Please address any replies to someone not very technical at all! Thanks.

I had to factory restore my 9 year old HP laptop today, which had been running Windows.

Obviously in the process I lost my Word software. Word is the one thing I use my laptop for. I did legitimately purchase Word around 9 years ago in tandem with the laptop. Miraculously I have found the original disc pack today, called Microsoft Works Suite 2006 (which has Word on disc one, it seems).

I've inserted those five Works Suite discs into the laptop today and run through an installation process. In doing so, it asked me for the product key, which I managed to find on a sticker on the back of the Works Suite box, and was accepted.

So far so good. However, when I tried to open a document saved in Word from my emails, it would only open it in a fairly basic Microsoft Office format, and lots of the commands I'm used to using (track changes, footnotes, notes etc etc) were unavailable. 

I inserted disc one from Works Suite again, the one that apparently has Word on it, but after clicking through a few screens I was asked for a product key again, and this time it sounded like a specific Word product key. I tried the same code that was on the back of the Works Suite box, but this time it wasn't accepted.

Anyone know what I'm doing wrong, or the simplest way for me to get Word back on my laptop?

Thanks so much.