This forum post will show you how to change the game speed (Speedhack) step by step through the third-party program CheatEngine. Each step is explained by a screenshot, press the Gyazo link to see this screenshot.

1. Download and install (at least) CheatEngine 7.0 on https://www.cheatengine.org/downloads.php , when installing a previous version, the game will not speed up correctly. ( https://gyazo.com/8912f27df4361c6f4bf630241e57991d )
2. Open Alien: Isolation
3. Open CheatEngine, and press the glowing monitor with a magnifier glass icon in the top left corner. ( https://gyazo.com/0b4f47dc0b19105aefd8f67e4a996e1f )
4. Select the Alien: Isolation process (note that the application code is different for everyone) , and press "Open" ( https://gyazo.com/b569ce415fd337c6a21f2f1f0726d705 )
5. On the right side of the CheatEngine window, press the tick box next to "Enable Speedhack" ( https://gyazo.com/e55a3de7b2e7c5dee14a8b52ca63af8d )
6. Now the "Speed" label appears, enter a speed here. (for a normal run, keep it at 1.0, for a 200% run, enter 2.0, etc.) ( https://gyazo.com/5e612416e128635a8323f6568509a4e4 )

Note that the game doesn't change the audio speed. Hence, on some places you still have to wait on the dialogue to end for a trigger to be hit (start of M5, M9, M15 etc.)

IMPORTANT NOTE! Close off CheatEngine and Alien: Isolation if you want to reset your speed to normal (1.0), any changes made in CheatEngine must be revoked by restarting the game and CheatEngine.

It is advised to not increase the speed above 5.0, after this the game becomes unplayable. Above 35.0 speed, the game breaks and the game slows down again. Be free to experiment!

Have fun running (really really fast)!

Also, some clips of speedhacks by Nolzze:

300% full run: 3500% hack & alien: https://www.twitch.tv/nolzze/clip/SpookyColorfulDiscFrankerZ & https://www.twitch.tv/nolzze/clip/FamousFuriousCrowPunchTrees