All around me klaxons are blaring and emergency lights are flickering. Unsure of where I am, I reach a thick glass window and, in an attempt to get my bearings, peer through the thickened glass, my wrench gripped tight in my right hand, ready for anything.

A screaming woman appears from my left, running across my field of view, her arms flailing wildly. Is something chasing her? In a few moments I get my answer: a mutated creature – half human, half I don't know what – runs down the hallway, following the woman. He – it? – stops, pulls out a shotgun and fires a shot, then ambles in the direction the woman went. Did it get her? What is this madness?

This madness, ladies and gentlemen, is the world of 1999's System Shock 2, one of the few games in all my years of playing games where I actually felt scared playing. Terrified, even. For many, it's one of the scariest games of all time.

Gamers who haven't experienced the scares of Irrational Games' and Looking Glass Studios' System Shock 2 are missing out on one of the best gaming experiences ever. But then, if you've played BioShock, then you've played the spiritual successor to System Shock 2. Set in 2114, players assumed the role of Captain William Diago, a soldier on the military vessel the UNN Rickenbacker, which is escorting the Von Braun. After investigating a distress beacon coming from the planet Tau Ceti IV, the Von Braun's crew is exposed to a genetic infection and integrated into a collective mind called the Many. It's up to the player to stem the spread of the genetic infection.

For its time, System Shock 2 set the bar for scares. Ghostly crew members materialise before you, lamenting their lost door cards but not realising that they're dead. That's not to mention the shambling infected crew members out to get you. Unfortunately, running System Shock 2 on today's modern computers, especially on that dog Windows Vista, is a bit of a mission. Eleven years on, System Shock 2 might be neglected because of an operating system we no longer use, but for many of us, it's not forgotten. So the next time you're playing BioShock and a splicer jumps out and scares you senseless, say a little prayer of thanks to System Shock 2.