I had this same issue, also on a pc, also trying to get driver support for a mac keyboard. I couldn't use the Command Prompt suggestion b/c apparently there was no .msi file (I also used 7-zip to look into the .exe for an .msi to no avail) - I assume it was a botched install because this isn't a mac. I couldn't use the default Windows add/uninstall programs tool, nor the one linked in other support articles (Microsoft Program Install and Uninstall tool). I tried reinstalling bootcamp hoping to use an uninstall/repair option, but couldn't because .. this isn't a mac - it said the install wasn't compatible with my machine. I have no idea how I managed to get a partial install in the first place, but I assume that's partly why there was no .msi file. I couldn't remove the program because it was running, I couldn't shut it down, and I didn't have any of the standard uninstall options available.