Follow these steps and maybe it will help.
1. Install the lateset graphics driver for you graphics card.
2. Install version of DirectX that came with your magicka installation. If you got magicka from steam, reinstall magicka from steam.
3. Install the version of the visual c++ runtime that came with your magicka installation. If you got machicka from steam, resinstall magicka from steam.
4. Install the version of XNA framework runtime that came with your magicka installation. Ect ect with steam.
5. If none of the above worked, install the lateest directX runtime from http://www.microsoft.com/downloads/en/details.aspx?FamilyID=2da43d38-db71-4c1b-bc6a-9b6652cd92a3&displaylang=en