I just entered into Rain with Selune and she's the first controlable companion in the game, but it seems she is entirely without use: She just stands in the back, doesn't follow me and doesn't attack, despite having her bow equipped and having sufficient arrows. Similar situation with David if I control Selune: Doesn't act on his own and only defends himself if hit.

I don't remember your campanions being this useless, so my first guess was that I've hit a key to disable companion-AI, so I've checked the manual - but nothing.
There is the D-key to en- and disable dispersal mode, but that is to make companions attack other targets than your own and since they don't attack at all it doesn't help.
There is also a function on the F-keys to limit shot projectiles by a ranged character, but David doesn't attack as well, so that's not it either.

Does anyone know what might cause this behaviour? Otherwise I must assume this is related to the gametime missmatch on actual CPUs which this game is notorious for and which is why I was so much looking forward to a release on GoG. :-\

Okay so if I mark both David an Selune and command them to attack an enemie, both suddenly get a gist of AI. For example they seek new targets if one dies, but only if I first commanded them to attack one enemy, otherwise they remain zombies.
I don't remember it that way but we know how memory can be.

I'm not sure if this is solved.

I've noticed this too, When "granddad" followed David he attacked intelligently, but once you get a proper party member they require you to Manually target a enemy for them to attack.

Me too I am "affected" by this problem. Is this normal? I recall the companions being somewhat more active during the fights. Like, not waiting for me to control them to do something...

I'm fairly, although not completely, sure it's supposed to work this way, that is, companions only start attacking when you select the whole party and click on an enemy.

I second that.

Really? It's pretty much impossible as it is. I don't remember the party members being quite so impotent.

I've come to the part where you enter Rain too, and also felt that the AI wan't doing anything. I remember the AI being somewhat more active.

I went and looked for some footage of the Dramcast version (good luck finding video footage of the PC version that isn't the gog version) and while the AI is a bit dumb in this clip, it acts on its own ackord somewhat. Though not much

http://www.youtube.com/watch?v=LN4ojiavQdQ

I also checked up on Wikipedia (yeah, not the most reliable of sources, but when it comes to games it's accurate the majority of the time) to see if the article mentions the AI. Which it does:

"The player may choose any character in his adventuring party to control, and the rest of the characters are handled automatically by AI"

So something is goofing the AI.

The real party members are supposed to act that way. It gives the player more control.
With 1-3 you can select a certain character. Backspace selects all 3 at once. Both is usually quicker than using you mouse.
You may have noticed the chains connecting the portraits in the upper left corner. They indicate, that "dispersal mode" is activated.
Press D to deactivate/activate dispersal mode.
When dispersal mode is activated and you tell 2 or 3 heroes at once to attack one target, they will all attack the selected target.
When dispersal mode is deactivated and you tell 2 or 3 heroes at once to attack one target, only the hero with the green frame will attack the target and the other heroes will select their own targets.

I was wondering about the same thing, however, actually it's the exact same way as I remember it from the original release. That's why I disliked the game a lot in the first place. I was rather hoping that someone would provide some actual information about how to properly use the party, maybe something I was unaware of more than a decade ago. Unfortunately it doesn't seem that there is anything to it. Party combat is just awkward in Silver. ;(