can my hunting knife be used as a bayonet?

The knife you received is a low quality hunk of lousy metal that is designed to look cool. The ring is there to make it look like a Bad A$$ military blade. Bayonets with rings like that are made for specific rifles. The ones that fit an M1 would not fit a M16 and the one for a M14 won't fit an M1 Carbine.

Quality - you can't buy a piece of good blade steel to make that knife from for what they are selling it for.

Up until fairly recently, all US military knives and bayonets were made from 1095 high carbon steel (Ka-Bar, Pilot Survival, M1, M4, M5, M6, & M7)

I have a pretty good collection of all US military knives and bayonets from early in Second World War

http://www.knifeoutlet.com/shop/10Browse.asp

Generally, high quality knives, which are designed to be sharpened to fine edge, are too brittle to be used as a bayonet. Bayonets are usually made of cheaper metal that cannot be finally sharpened, but can repeatedly stand up to being thrusted on the end of a rifle into twisting bone, sinew, and equipment. Sounds like you may have a cheapo knife that is made to look cool.

I don't think the zombies will give a flying f u c k if they are bayoneted with a Kabar or a steak knife.

with the power of duck tape, any knife can be attached as a bayonet.

Getting set to repel boarders?

Face*palm