Before installing OFP, make sure that your system has no IRQ conflicts. Failure to do so can cause all sorts of problem, such as lost sound, multiplayer connection problems and more.
Sometimes, IRQs are shared amongst devices built on-board on your PC's motherboard. These can include sound, video, network and other devices. Usually, these IRQ settings cannot be modified. In some of these cases, the only technical solution is to install a separate normal device card and disable the one on-board.