I changed the grafic cards from Matrox to Gforce 4. First I changed back to VGA, than via software I could deinstall (remove only) the matrox driver. The routine said I schould switch the pc off, what I did. I changed now the AGP cards and started the pc. Out of the sudden there is a message saying "windows root/system32/hal.dll" is missing or destroyed, however I didnt touch anything. XP Prof and it is a Standard PC configuration. Any help?