Ok I have messed with this for a while and saw the pattern of when to rename the folder that rob435 has suggested.

First run the ATIi mmc 8.1 setup as usual with your root:\\Documents and Settings\username\local settings\temp\ folder open. And then observe as the installer begins to create the folders. you should see the following :

Keep and eye on the file highlighted above, it will vary from computer to computer i am sure but take note of the .tmp extension. After a small while you will notice that it changes to the following :

Now notice the .rra extension. As soon as it changes  from .tmp to .rra changes this is the key moment to rename folder.

Just to refresh those of you who have skimmed passed rob435's post ; our goal here is to rename the folder {28ADA52D-B7AF-442C-8B7F-CEB9ECC28078} to something else.

I would suggest simply adding a character to the folder name as follows :

From {28ADA52D-B7AF-442C-8B7F-CEB9ECC28078} to for example {a28ADA52D-B7AF-442C-8B7F-CEB9ECC28078}. This way you can easily restore the folders name later (this is important)

If you have done everything correctly, the setup screen appears with the license agreement and all. This is when you should restore the folder {a28ADA52D-B7AF-442C-8B7F-CEB9ECC28078} to its original name (i.e remove the a). Click NEXT a few times, (remember to perform a custom install) and check the TV option and voila you have MMC 8.1. I have done this on a first machine with a 90% success rate.