kbdstub.exe is a process known as key watcher. It belongs to HP's Keyboard Handler and its main function is to watch multimedia keys on HP keyboards.
kbdstub.exe is a non-Windows system file and it starts upon Windows start-up. It has a visible window but without file information. Technically, kbdstub.exe is potentially dangerous for your computer since it is located in the C drive's sub-folder C:\\program files\.