I can think of at least 2 different ways:
using Task Manager (Ctrl-Shift-Esc), select the process tab, look for a process name cscript.exe or wscript.exe and use End Process.
From the command line you could use taskkill /fi "imagename eq cscript.exe" (change to wscript.exe as needed)
Another way is using scripting and WMI. Here are some hints: look for the Win32_Process class and the Terminate method.