BOBWY

I have a dual boot PC with Win 7 and Win 8.1 ,ocasionally I can't boot into Win 8.1 and a message comes up that a File:windows\system32\drivers\msisadrv.sys is missing Status0x0000242 In the past instances I had to re-install Win 8.1 ,what a pain! How can I re-install the above file without re-installing the wholle Win8.1 system ? Operating system:Windows 7 Home Premium (64 bit) Service Pack 1 System root: C:\Windows Available physical memory: 8190 MB CPU: AMD Athlon II X2 250 Processor Drive Info: C: 111.79 GB F: 931.51 GB G: 931.51 GB Internet Explorer: 11.0