How do I get cat pee out of carpet?

My poor sick cat has pee’d on my wall-to-wall carpet. I didn’t notice the smell as it’s in a room I don’t frequent. However, my neighbor has complained he can smell it (through the wall!). I put my nose down to the offending area, and lo and behold, it smells like pee.
I don’t know how long she’s been peeing there, so it may be a few months old (gross, I know).
Anyway, I tried a product called Knoc-out and it didn’t get rid of the scent completely. I’m now trying Simple Solution Extreme. Has anyone had any luck with this or anything else? I need to get rid of the scent completely so she doesn’t go there again.
Has anyone heard of heating up vinegar and leaving it in a bowl in the room to help eat up the odor?
Any tips to get rid of cat pee smell is appreciated!