Failed to Validate BAM Portal Web Site (BAMPortal)

I have a clean IIS6 with only Default Website in it.
Configuring biztalk and got stuck on BAM Portal configuration and it shows a cross on BAM Portal Web Site with Default Web Site selected in the dropdown. The error is as per the title of this question and also in the following screenshot:

I searched on the internet and found that it was related to IIS6 Management Compatibility feature. I found out that this feature was already installed. but still I uninstalled it and reinstalled it back, restarted PC, IISReset. but the problem still persists.

What else should I do to resolve this issue??

Regards