Weakness to Normal Weapons is bugged. It has no effect at all. Resistance to Normal Weapons works fine, but Weakness to Normal Weapons does not increase the amount of damage iron/steel/etc weapons do to a character.

I want to use this as a Bosmer racial but I have to fix it first.. where are the scripts for magic effects stored?

I was under the impression that the weakness to normal weapons effect worked but was only useful for the purpose of countering resistance to normal weapons. That if it was used on a character who had no resistance to normal weapons, it would do nothing; but used on a character who did have resistance to normal weapons it would lower that resistance by the amount of the weakness effect, but not beyond the resistance effect.

All that said, I can't find that info as I'm looking now, so maybe I'm just off my rocker.

You are correct: Weakness to Normal Weapons does counter resistance, but that's not what the wiki or the manual says, so I maintain it is bugged

Fair enough.
As for how to modify it, I know not. Hopefully someone will though. Best of luck.

I don't believe we can alter the Scripts for Spell Effects, unfortunately.

Now what you could do is seek out Health Damage to the NPC, and then simulate additional damage based on the Health change-- my guess would be OBSE's event Handlers would be the best way to do this, but I don't know enough about them to help (the basic way, of just checking the NPC/Player's health every frame has, as far as I know, no way to distinguish between damage types without scripting each NPC individually, making it messy and overly-complicated).

http://www.tesnexus.com/downloads/file.php?id=34841 fixes it rather nicely, among many other things.

Wow, that's a serious mod. I particularly like the diminishing returns system on Resists.. much better than the clunky system I'm using. I'll give that some serious thought..