dwmapi.dl trying to be installed all the time. Firewall alert. Saf

S.G.

Hi,
I am using Vista Home Premium, coming instaled on my Dell XPS notebook.
I lately formatted all, pc is clean (I suppose), no programs installed yet.
No windows updates, I am downloading the standlone SP1 because I am tired to
downlod it all the time that I have to format.
So, I use Comodo Firewall. Version 3.
Its Defense+ function alerts me that IE, than WMP, and then Firefox are
trying to install a hook (no idea what a hook is), which is dwmapi.dl (not
dll), unders system32...
What is that? May I allow it?