"lI'qu' De'wI' vIghunbogh."
Translation:The computer that I programmed is very useful.
I have programmed means that you've finished programming it. When you want to indicate that you've finished an action, you need a perfective suffix:
computer which I have programmed, computer which I programmed
Unfortunately, this course incorrectly teaches that any English simple past tense sentence can be translated into Klingon without considering whether the action is completed or not. In this case you're probably trying to say that you programmed it and now that programming is done, in which case the English given by this lesson, the computer that I programmed, really needs to be translated by Klingon perfective -pu' or -ta'. Without the perfective suffix, it means something more like computer which I program; maybe your job is to program it regularly, or maybe you're in the middle of programming it.