Hi...
I have Vista Home Premium, just formatted, no strange stuff installed, no updates yet.
Comodo Firewall, well, its Defense+, tells me that Internet Explorer, then Windows Media Player, then Firefox, are trying to install a hook (what is a hook?), dwmapi.dl (not dll!), under sistem32...
Is it safe??????

Hello and Welcome to PCHF

Could be a Comodo false/positive. Look over this
Problems with MSCTF.DL

Thanks Geek,
I think I agree: I had this same opinion by two other people (one on Hijack forum, the other is a friend, a Dell's technician who says that sometimes Vista in its error messages call "dl" the "dll".).
And, as I was installing the SP1, I had to put COmodo on Install mode, and I was not able to block again the dwmapi.dl instllation. Well, it installed as dwmapi.dll. It is by Microsoft, and yes, as many have suspected, it is a part of the desktop manager.
SO, it should be all ok.
Now I just have to see why the SP1 gave me the 0x800F0826 error message and did not installed.
May be Comodo.
Ah, by the way, a-aquared found a low risk riskware in program files\comodo\firewall\s1.tmp, called Riskware.adtool.web32.mywebsearch.bn
and avira found a trojan, Spy.banker.vk.1, on 2 gif images in a offpage site I had downloaded. Anyway, the first can of course be involved, by the second was on another partition, and I had never opened it after the formatting...
Mmm...
Tmp sounds like a temporary file, something that Comodo recollected. I didn't knew that firewall recollected things.
Mumble...
A guy in Comodo forum says that "dl" extensions may be Sub7 malware variant.
But, anyway, it said it wanted to install hook dwmapi.dl, but it installed dwmapi.dll... by Microsoft.

Sir Joe,

Was there an underline after the .dl like dwmapi.dl_ ?

Mmm, unfortunately I formatted all again , and I do not remember 100%, but 90% the answer is no, no _.
Why?
Take a look to what this guy answered me here:
https://forums.comodo.com/help_for_v...4015#msg174015, reply nº19...

Interesting
It only takes 12 seconds for an unprotected computer to become infected on the internet

Mmm, I still am not sure it is a malware.
But I do not know how to be sure.
I formatted all, and any new program or windows function which I use for first time still try to install hook dwmapi.dl.
If I say not, I do not see nothing bad.
If I say yes, I see dwmapi.dll installed in system32.
I guess it is not malware.
But, apart Avira, Comodo, Windows Defender and Avg Anti-Rootkit and A-Squared free, what else can I use?