Hi Ash,
Here's a link to a download of some version of Office Pro 2007 that seems to include a free trial which suggests that you may be able to install it as a trial and then use the genuine product key to activate it fully (if it's close enough to the same version for that to work and if trial upgrade activations are still working).
Microsoft Office Professional 2007 - Free software downloads and software reviews - CNET Download.com. But I think it's worth a try and is the best safe and legal and I hope free option I could find.
I STRONGLY recommend against an FTP ISO site (like a file sharing site - especially if using torrents) as that's one heck of a good way to get infected or get a bad/defective product or get one with activation or genuine validation issues.
I hope this helps.
Good luck!