Question about microsoft office product key usage

Hello,

I am interested in buying one microsoft office software (preferably 2004) but I do not wish to spend over 120 euros especially for an older version.

(I have tried Openoffice, Neooffice which I found hard to use and iwork '08 which looks very nice and works fine but lacks some features of microsoft office.)

I found some used items on ebay but I am not familiar with the usage of the product keys.

So my question is this: if someone has used a product key and then removed the software, would this mean that I can no longer used it on my mac?

Thanks in Advance

 

Thanks for the immediate response,

I am used in working with microsoft office for about 10 years now and even though I had no problems switching to mac, I encounter several other problems when starting using office suites other than microsoft (iwork was the easiest one, but I had problems with table of contents).

So, I am going back to microsoft solution, I think is the better one but overpriced, that it is way I am looking for a used cd.