Hi! from what i know, we use "there is" when we talk about the existence of something in a particular place. In your sentence, something is wrong somewhere(wether hardware or software wise) in your computer. You'll notice the difference because we use "it is" generally to talk about things that have no apparent subject the weather or the time, so we need to add a subject "it" followed by a conjugated verb (in this case the verb "to be"). "it's hot outside", "it's 4 in the morning" In your sentence the subject already exist(your computer) so there is no need to add the "it" Hope this was helpful :)

This is an interesting question. I am a native speaker and I have never thought about this.

Dear if you use” it is something wrong with my computer” The meaning here will be totally different that “ there is” When you use there is it means the existence of a problem but if you use it is the meaning will be committing something with your computer