Simple RAW for 3.5: 38 pages, and I still don't know how to play D&D

[Troacctid]

Q 112
The "hand crossbow focus" feat from drow of the underdark says that it counts as the weapon focus feat for anything that has weapon focus as a prerequisite.
Does that make it count just as "weapon focus (hand crossbow)" or for any kind of weapon focus prerequisite?

The short answer is that it would only count as Weapon Focus (hand crossbow).

The long answer is that technically, there is no such feat as Weapon Focus (hand crossbow). The name of the feat is always just Weapon Focus. The parenthetical indicates the particular weapon chosen for the feat. So if a prerequisite calls for Weapon Focus (longsword), Hand Crossbow Focus would not count for it: you do have Weapon Focus, but you didn't choose the longsword as the associated weapon.