Vista - Problem:Vista:Compaq: Preloaded OFFice v New Purchase of Office

I found and joined the forum about a fortnight ago, so Greetings.
I am here now because I was floundering in cyber space and brought here by Hermes , I guess, because he knew that last June, 2008, another mortal had the same problem but no solution..........see attached file

Background info by way of introduction...I am the sys administrator:

18 month old Compaq SR5129UK preloaded with VISTA, and MS OFFICE trial
which I failed to get to work so I've managed with WORKS meanwhile, & a grudge.
....the problem of having been the one in control of my own PC for about 20 years

This week I bought Home/Student Office 2007 in the hope of getting to the point I was at over a decade ago : being a happy MS s/w user.
Then my problems began.

The installation started and almost instantly took a dive and said it had failed.
I checked the disk on an old PC and it is fine.

I assumed the pre-installed version could be the problem and tried to uninstall, unsuccessfully ...tried turning off (& restoring) user a/c ctrl in case that would help but no.

Bottom line is that there are still over 200mb of s/w which I cannot remove or use and a legal CD that cannot replace the existing version.

I use my PC almost non stop for all manner of things so regard it as a workhorse (now I no longer have to be a system administrator for scientists like myself)

I realise if I had actually NEEDED Word when I got the PC & persevered I would not now be looking for a solution and understanding from fellow mortals

So to recap:
The attached message, that I saved to file, came on my screen today
I turned to you for help & have tried to give useful clues.
I'll continue my endeavours in case no one can help
***
I hereby promise when I get a new PC with Windows 7 , when there will be no user problems, I shall spend days learning the system and watching until I feel in control ...just like the old days

If I get help I'll be grateful and appreciative
I can go on giving it to others, I shall be equally grateful