The leading actor is Ken Chang Chi Yiu. Here he is(screenshot from "SPL"):

But this movie is not even listed at his filmography.
http://hkmdb.com/db/people/view.mhtml?id=12553&display_set=eng
Instead of this there is listed Ken Chung Siu Hong at Ken Chang's role:
http://hkmdb.com/db/movies/view.mhtml?id=10292&display_set=eng
But if we go to the Ken Chung's page...
http://hkmdb.com/db/people/view.mhtml?id=14254&display_set=eng
...we'll find out that he looks the same as Danny Chan Kwok Kwan
http://hkmdb.com/db/people/view.mhtml?id=14150&display_set=eng
Well, that's because there is another error

On Ken Chung's page actually posted Danny Chan's image.
And the real Ken Chung looks like this (not sure for 100%, but seems that it's him):

It seems that Ken Chung has not been in Era of vampires at all.
Only Ken Chang.
No wait, Danny Chan was also in this movie. Let's see Danny's images from that movie:

http://hkmdb.com/db/images/movies/10292/EraofVampires+2002-14-b.jpg
http://hkmdb.com/db/images/movies/10292/EraofVampires+2002-4-b.jpg
Hmm, that doesn't look like Danny.
This is actually.....tam-ta-da-da.....Ken Chang!

So, once again

Ken Chang - leading actor in Era of vampires:


Ken Chung:

Danny Chan:

