I am a hardcore fan of Alien, and Predator since I was tiny (Talking since like age 7) and one sunny hot day I went over to shop with my mum and there it was. Aliens vs Predator demo on PC Format. Shat a brick, and begged my mum to buy it for me- was a cool R19 back then.
Making a long story short, I didn't have a good enough computer to run it (at all) and a couple of months after I even bought the full game even though I couldn't play it, my parents eventually got me an upgrade. Played it it to death on every species, till I could fly through Director's Cut. My favourite gameplay as the Predator vs humans, like in the movie. Switch to thermal view, targeting an oblivious marine with the 3 laser dots, and blasting his upper body into many pieces and watch his severed limbs twitch on the ground. Nail their heads into the wall with the speargun. Alien gameplay was obviously also a favourite, chowing the heads off of civilians crying and begging for mercy. I was a sick child.
Game came out on 30 April 1999 after the 1994 Jaguar version which also had 3 campaigns (Alien, Predator, Marine). What annoyed me about it was that there was no save game feature, which was later added in the Gold Edition in 2000.
There was a version of it released in 2010 called Aliens vs Predator Classic 2000, which can run on modern computers- so I'm assuming up to Windows 7 at least. Has all the added content from Gold Edition and has multiplayer- con is you can only get it from Steam as far as I know.
Frankly, one of the scariest games I've played (Marine campaign anyway), and of the most fun multiplayer games.