Old Pet Stains

[snowyowl]

Our dog was very stubborn when it came to house training. It took foreeeever and she was sneaky. I cleaned thoroughly after every accident, and it seemed like there was no permanent staining. However, the first summer after she was trained, as soon as it got warm, the stains appeared and started to smell. I rented a wetvac and that seemed to make things better (not gone, but better). Now it is getting warm again, and the stains and smell have reappeared! After a year and a half! I'll probably end up renting a wetvac again at some point, but it doesn't make sense to do it right now because we are moving soon and I'd rather do it when there is no furniture in the house. Any tips that will work on the smell and the stains while the landlord is trying to show our house? 
We have lived here for quite awhile and don't really mind if we don't get our deposit back because the landlord wants to replace the carpet. But I don't want people to be put off the house by staining or smells. Our landlord has been very kind and accommodating to us over the years.
It might sound like the dog is sneaking a wee in this same area, but the stains all appeared at the same time in several different places on the first warm day. They are dry, but the warmer outside the more smell there is.