dtgreene: The version contained in the Wizardry Archives collection is the one that has a nasty bug involving stat growth, one where at least one player has reported having young characters die of old age.
The DOS floppy version, I believe, is quite playable without the same flaw. I do not know what bugs, if any, are present in this version.
The Apple 2 version suffers from worse graphics and a worse interface, but it has the advantage that the identify glitch is present, allowing you to break the game if you so choose. (The glitch only happens if you press something outside the 1-8 range when having a Bishop identifiy items.) This version has a few other quirks, like the fact that you can encounter 2 groups of enemies at once on the first floor (in other versions, this doesn't happen until at least the second floor, though I'm not even sure about that), and that spells can be cast during the surprise round (this can be unfair if a group of mages ambushes your party). Also, there are cheat programs for the Apple 2 (like WizPlus) and even some that let you make custom dungeons and monsters; I am not aware of similar programs for the DOS version.
Avantgarde: Do you know how alligment works and how it can change? I have really no clue why my priest turned good. We were killing everything.
In the Apple 2 version:
A friendly encounter will only occur if you have at least one good aligned character in the party.
The chance of a group of monsters seems to be in the range of 1-31% depending on the type of monster. (The code is a bit convoluted; the random number (1-1)) must be at least 50, but not more than a monster type dependent value.)
If an encounter is friendly, all monster groups are automatically identified (in case you choose to fight them).
If you choose to fight, there is, for each good character in the party, a 1/2000 chance that the character will turn evil. (The game checks to see if the random number is exactly equal to 565; this smells like a bug to me.)
There is no code to change a character's alignment from evil to good, even if you somehow get into a friendly encounter with an evil character in the party.
In other words, it appears that what happened to you *can't* actually happen in the Apple 2 version (barring some memory corruption bug, but the only one I know of (the identify bug) can't change alignment, I believe).
I'll look up the code for Wizardry 3 in a moment, as I wouldn't be surprised if the behavior changed, and if the changes also appeared in other versions of Wizardry 1.
Wizardry 3 (Apple 2 version) did change some things:
There's some check (looks like it might be comparing party and enemy alignment) that can prevent an encounter for being friendly; otherwise, there's a chance (3-50% (or is it 3-30%?) depending on enemy type) of the encounter being friendly (and this is calculated in a more straightforward way than in Wizardry 1). Again, the enemies are identified when this happens.
If you choose to fight, each good character has a 5% chance of turning evil; if you choose to leave, each evil character has a 5% chance of turning good.
It seems that they really cleaned up the routine between Wizardry 1 and 3; the Wizardry 3 routine makes more sense. Isn't this behavior more sensible?
This seems to be the only thing that can change a character's alignment.