From Google Answers:
An inexpensive product I'm going to recommend is called Nature's
Miracle and it can be bought at most pet stores, such as PetCo or
PetSmart.
It's all natural and will not harm the carpeting, it removes all
organic stains and odors. Semen is not listed as one of the stains it
will remove but the description states: "It also removes stains and
odors caused by foods, blood, vomit, feces, grease, dirt, grass,
smoke, perspiration and all other organic stains and odors."
Description
Nature's Miracle Stain & Odor Remover contains the same ingredients
that nature uses to rid organic debris from the earth's
surface--enzymes. It eliminates all stains and odors from pet
accidents--even urine odors that other products fail to remove--or
your money back. Safe for use around children and pets and on colors
because it's non-toxic, non-flammable, non-caustic and non-acid. It's
safe on all water-safe surfaces. Nature's Miracle Stain & Odor Remover
eliminates urine odors completely with no perfume cover-up odor.
Discourages pet resoiling in same area. It also removes stains and
odors caused by foods, blood, vomit, feces, grease, dirt, grass,
smoke, perspiration and all other organic stains and odors. Nature's
Miracle consists of billions of nature's enzymes that turn organic
stains and odor causing material into a liquid you simply wipe away.
Plus, only Nature's Miracle contains exclusive ingredients that speed
up and greatly increase the effectiveness of the enzymes--and also
helps neutralize acids in urine, vomit, and feces which helps restore
color and lustre to carpets and floors that have been stained. For use
on carpets, floors, furniture, clothing, cages, litter boxes, and pet
living and sleeping areas.
Also, get a room! :getdown