I dont know of many in the pc software expect for maybe matrox related products or adobe premieire. virtual dub comes to mind but thats a freeware version and may have a plugin, who knows.
I do know this for good keying
keep the stage 15 or feet if you can from the screen itself or just enough to hide shadows.
3 good tungsten lights for like $15 each at a warehouse/hardware shop make for a great setup.
DVCAMS using either blue or green or alpha channel mattes from DV footage have a harder time getting the correct key.
eg the fluffy stuff near the actor or object your keying.
shake by apple has two industry standard keying application tool components that allow you to do great keying in both the green abd blue spectrums as well as combining them together. try this link i think http://www.apple.com/shake/quicktour/keying.html
getting a good key is a tricky process but its all about a clean line and no shadows on your key areas.
the lighting for the actor/object has to be setup for the scene your dropping them into,
good keying takes a few goes to get it correct.
If no-one gives your an answer to a question you have asked, consider:- Is your question clear.- Did you ask nicely.- Are you showing any effort to solve the problem yourself