From: Zagreb, Croatia
This is issue with UAC (can safely presume that you have either Windows 7 por Windows Vista)...
The WitE Matrix installer is trying to write into registry and UAC is preventing that (and there might be issue with your account's permissions to do system stuff)!
Thus please do:
Run installer with "Run as Administrator".
Restart PC after that.
Try playing game normally!
Prior Preparation & Planning Prevents Pathetically Poor Performance!
A & B: WitW, WitE, WbtS, GGWaW, GGWaW2-AWD, HttR, CotA, BftB, CF
P: UV, WitP, WitP-AE