One thing I will add to this conversation is that you could try a fast-ferment test. Take a sample of the beer (at least enough to fill your hydrometer tube) and pitch an entire pack of Nottingham in it. Since you're not drinking the sample and not worried about oxidation, shake the crap out of it and leave it at room temperature for a week or so. Check the gravity again and if it hasn't moved with that much yeast, then you can be 100% sure that there aren't any remaining fermentables in the beer and it only cost you a few bucks.
On the other hand, if you do find that it fermented drier, then there is hope. In this situation, I have tried just about every option out there (multiple packs of yeast, starters, etc.) and my only success came when I pitched a huge slug of healthy slurry from a local brewery or brewpub - on the order of a quart or more of a workhorse yeast like 1056. Sure, it's overpitching, but I was able to take one of my larger (1.130+) beers down another 15 points using this method.
I also agree with the others who say you should set this aside. Some beers that were cloyingly sweet when they were young turned into great beers with a few years on them.