laundry room smell

[yousignup]

OK, it's more of a laundry cupboard, with a door to close on the washing machine. Never any problem smells before... until two weeks ago when something went wrong with the washer tube and it flooded, twice.
There is a small, old drain in there, which is hardly ever used, and the water went down there (an awful lot of it). Now whenever we close the door, there is a terrible smell of open drains, really overpowering. The drain isn't blocked, just extremely old.
Any idea of cleaning products to get rid of the smell? Window is nailed shut so there really is no ventilation. I want to close the door to shut out the washer noise and also hide it, as it leads directly on to our dining room. However when I do that, the room becomes full of the sewery stink.
Any suggestions?

Come on! Nobody cares about my dining room smelling like a sewer?

Could it actually be the pipe to the washer that's smelling?? Could you get some washer cleaning stuff and put the machine on with it in?
I recently ripped my laundry room apart looking for a smell. Turned out to be ds football boots

Sounds like it needs a bloody good flush! If the drain isn't used it probable had caked on gunge that's now all wet . I'd get that window de bunged too. Bleach and hot water? Biological washing powder/hot water?