Even if it had completely may times the drivers for the build in devices are not properly used. I know win10 refused to use the win7 drivers and the generic ones did not work for people when win10 first came out.
First step is to acquire the proper device drivers for your machine. You likely want all of them because you may still have issues with other stuff like USB ports or sound drivers. The manufacture should have drivers for windows 8.1. You download them to a cd or flash stick and install them from there. Exact process will vary a bit but most manufacture have a executable that will install the driver. Worst case go through the device manager and tell it to update the driver and point it to the ones you downloaded.