You've gone through most of the things to check, but one more thing to try: something may have gone wrong with your Windows C++ runtime files, so it's worth trying to reinstall them. You can find the links to download it at
https://support.microsoft.com/en-us/...al-c-downloads - most likely you want the vc_redist.64.exe one, unless your Windows 8 is the 32-bit version, in which case take vc_redist.x86.exe.