You keep the same HP when you change class; however, it doesn't give you more HP in the long run. The way it works is this:

* When you level up, the game re-rolls your HP for every level, not just your current level. For example a priest or samurai gains 1d8 HP (plus vitality bonus) per level, so on reaching level 3, the game would roll 3d8 + 3x vitality bonus (so at 17 vit, which gives you +2 HP per level, the game would roll 3d8 + 6).
* If the roll is higher than your former max HP, that becomes your new max HP; if not, you gain only 1 HP from level up.
* Because of this, a character who has just changed class will gain only 1 HP per level until their level has caught up to their HP. On the other hand, getting a vitality increase late can lead to a large HP gain, and you don't need to have high vitality to get high HP in the long run.

HP per level (in Wizardry 1 Apple 2 verision) is as follows:
Fighter/Lord: d10
Priest/Samurai: d8 (but Samurai are considered one level higher, so a level 3 Samurai with 17 vit gets 4d8 + 8).
Thief/Bishop/Ninja: d6
Mage: d4

Vitality modifiers (per level, no minimum):
3: -2 (looks like an integer underflow could occur, making it theoretically possible to have 65535 HP after level up, but this can be a bit risky to pull off and might be fixed in later versions)
4-5: -1
6-15: 0
16: +1
17: +2
18: +3
Any other value is 0.

Do note that having Vitality decrease below 3 at level up will trigger death from old age, which will cause the character to be LOST forever.

Thanks for such good answers :D
Last question before I start to roll new characters in the dos floppy version.

If I change my Fighter to a Priest for exemple. Will that priest be able to wear any weapon and armor? Will the priest have the 2 to 3 hits per attack as an experienced fighter has.

No. The only thing that you keep when changing classes are HP (which isn't as useful as you might think, as I have mentioned above) and known spells. Your age will increase, and your stats return to minimum racial values.

Hence, the only class changes that make sense are changes from a spellcasting class to another class, or changing to a class that is difficult or impossible to create.

Note, however, that if you know one spell of a level, you can learn the other spells of that level by leveling up, even if you changed class since learning a spell of that level; hence, you don't need to learn ever single spell before changing class. Once you have at least one spell of every spell level you care about, it's time to change class. (Be aware, however, that with low INT or PIE, your chance of learning the missing spells at any given level up will be lower.)

(Incidentally, in the Apple 2 version, it is possible to learn LOKTOFEIT early thanks to the identify glitch; doing s will allow you to learn the other level 6 priest spells regardless of class, including most notably the MADI spell.)

So I have played the DOS floppy version for a couple of hours now. I believe something is terrible wrong when it comes to examine chests and disarming them. My Theif is complety useless. Seems to never get it right. Using Calfo with my priest also seems broken. Perhaps 7 of 10 times calfo has giving me the wrong trap.

This never happend in the C64 version. Calfo were more or less a sure thing. My Theif could open chest most of the times. I see no point in opening any chess at all now in this version

Nobody else that have noticed this?

But I dont want to quit. So shall I drop my theif and get another fighter? Will I miss alot of good gear if I dont open chests?

If you don't open chests, you will miss *all* gear, except what can be bought in the store. There is no other way to get equipment in this game.

Also, does your Thief have at least 16 Agility? The chance of a thief correctly examining a chest is (supposed to be) 6 * agility (for Ninja, only 4x), capped at 95%.

Just in case, try having other classes inspect and disarm chests; maybe some other class is better at dealing with chests than intended in this version?

If what you're saying is accurate, then the DOS version is also buggy. It sound like you may have exhausted all the early microcomputer versions of the game, and may be in a situation where there is no way to get a decent bug-free experience for this game without playing one of the good-looking console ports. (Note that you can change to classic dungeon graphics in most console ports.)

By the way, the NES version isn't bug-free either; AC doesn't work properly for your party. The Super Famicom version might be the best, or maybe the PlayStation version (the PSX version of Wizardry 5 does have its own bug; BACORTU doesn't work).

I guess we have a maze of twisty little bugs, all different.

My Theif had 16 but it droped to 15. So he is quite good on paper I guess :)

Well. I dont know what to do. Maybe play the Ultmate Wizardry Collection. Or play the original. Just make a backup before each expedtion and if the party is wiped out in a mage/priest suprise attack... reload.

I will try to roll a new theif and give him 18 in agility. See what happens.

Are you an expert on Bards Tale too?

18 agility is a good idea; if a character has 18 in a stat, and the stat would decrease at level up, there is only a 1 in 6 chance that it will actually decrease; hence, you need to be really unlucky for it to be a problem.

I could consider myself an expert in the classic Bard's Tale games, though of course I haven't played every single version of them. (I have played 3 of the 4 classic versions of Bard's Tale 3, however; the DOS version of BT3 should be avoided (apparently, the Amiga version, which is the one I haven't played, is also bad).

Yeah. I put it at 16 so I could put more into Vitality and Strength. But that seems to be a waste of points. The theif will never be any good at fighting. Not even a slightest.

Regarding Bards Tale. I played through the first one on a C64. There were a bug in that version that made the class Hunter useless. Overflow bug i think. I loved the game but i am really tired of buggy games.

I want to play Bards Tale 2. So which version should I play. I kinda want to play the C64 version but if that has alot of bugs I will choose another one.

For BT2, I think the Apple IIgs version might be best here; it even has an automap!

The game has some balance issues. From what I hear, in the C64 version, after about halfway through the game, your characters can't hit the enemy with physical attacks. In the DOS version, for a fair portion of the game, enemies are unable to hurt you (assuming you have decent equipment and are at an appropriate level).

Bug wise, I am not sure about the C64 version (I haven't played it except to try it briefly), but the DOS version, while playable, does have a few bugs. In particular, some bard songs work differently than they should (the wrong song makes it dark when it stops, for instance, and bard song 7 plays the incorrect tune unless you turn the sound on and off). There's also an overflow in the Hunter's critical rate that sounds like the one you experienced in BT1 (DOS BT1 doesn't have this particular overflow bug), but you can work around it by not leveling the Hunter past that point.

For BT3, I find that the C64 version is the least buggy (though one poster has mentioned that a certain clue is missing in this version). The Apple 2 version is almost as good (though apparently the disk images you find on the internet have corrupted graphics); it has a few bugs not in the C64 version, including a major exploit that I remember discovering by accident back in the day. As I mentioned, the DOS and Amiga versions should be avoided (though somebody *did* make a patch for the DOS version that fixes at least the most serious of these bugs); for instance, special attacks don't work at all (for example, dragons don't breathe fire the way they're supposed to).

I like to draw my own maps :D It is a really nice experince.
The Apple II version of BT2 might be the best in that case? Play it wih Applewin. Or maybe the Apple IIgs version and dont use automap.

When time comes for BT3 I will go with the C64.

So I notice :D No problem in disarming traps with 18 agility.

Another question. I have reached the 7th floor. All my characters are between lv10 - 13. Damn nightstalkers and lifestealers... To the point. I stumbled into a room with 3 Fire Dragons. Guessed that this fight wouldnt be easy. Tried to fight one round, the other rounds to flee. Failed and my party died.

If I was to assemble a rescue team. Will my dead party be just outside the room with the dragons? Or do I have to defeat the dragons to rescue the dead party?