Anielaric did you try this?
1) completly removed LOL installations, and every file conneted to LOL. Restarted windows.
2) installed new graphic cards drivers
3) installed directx (not this one which is added to installation of LOL, I used this one -> DirectX 9.27.1734 (9.26.1590 worked aswell). Restarted windows.
4) installed service pack 3 (both cases, my friend and bro had windows xp). Restarted windows.
5) Installed brand new LOL (declined option of installing directx from LOL installator)