I'm using Office 2013 Professional on Windows 8.1. Till some days ago it worked. Suddenly with no obvious reason (didn't install or change anything) whenever I try to run any office program I see a window titled: officec2rclient.exe - Bad Image. Detailed error message is: "C:\Program Files\Microsoft Office 15\ClientX64\ApiClient.dll is either not designed to run on Windows or it contains an error. Try installing the program again using the original installation media or contact your system administrator or the software vendor for support. Error status 0xc000012f." I tried uninstalling or changing the program through the control panel - doesn't respond, nothing happens. I've checked the Windows event log and I can see that the uninstalling command failed due to the same error. I also tried to run the Office installer again, however it fails as well with the same error message. I'm not sure if this due an corrupted Office installation/update or if I've been hit by a virus or other kind of malware here. My antivirus (EMSISoft Internet Security) didn't find anything as well as Malwarebytes Anti-Malware, however there is still a kind of a "bad feeling" that my PC isn't 100% clean. How can I make sure that my PC isn't infected?