So, when I wanted to go through FEAR a month or so back, I decided to go through my Device Manager to pinpoint what exactly caused the FPS to drop under the Human Interface Devices.

The culprit was the three "vendor-defined devices". So I made a script so only disable those three devices when you start the game, then re-enable them when you quit.

Keep in mind this might be machine/setup specific, but I'm sharing it anyways. As an added bonus this also allows you to keep your volume and player controls. It will only disable special mouse settings and any extra side keys your keyboard may have (in my case the G1 - G6 keys).

This will require you to have "devcon.exe" in your FEAR folder and it must run as admin. If you don't have devcon Google it.

Make a batch file with this:

devcon disable "HID\VID_046D&PID_C24D&REV_8001&MI_01&Col03"
devcon disable "HID\VID_046D&PID_C080&REV_9501&MI_01&Col04"
devcon disable "HID\VID_046D&PID_C080&REV_9501&MI_01&Col05"
FEAR.exe
devcon enable HID\VID_046D*
devcon restart "HID\VID_046D&PID_C24D&REV_8001&MI_01&Col03"
devcon restart "HID\VID_046D&PID_C080&REV_9501&MI_01&Col04"
devcon restart "HID\VID_046D&PID_C080&REV_9501&MI_01&Col05"

To use it with the expansions, put devcon.exe in the expansion folders, along with the batch file, and just change "FEAR.exe" to "FEARXP.exe" or "FEARXP2.exe"

Again use at your own risk I suppose. My keyboard is a Logitech G710+ and my mouse is a Logitech G303

Is this fixed in Windows 10?

I played for half an hour and no slow down.

But I do remember having this issue under Windows 8.1.

EDIT: I let it run for 2 hours and still no slow down bug. Can anyone else confirm if this issue is still present in Windows 10?

I still get it in Windows 10.

Still happens for me in Windows 10 (the reason I posted here).

That's weird.

Funny, I wanted to video capture this bug, but now I can't replicate it LOL

I'm downloading the Steam version now, maybe there is a difference.

The mouse I use is a G400 and I have the Logitech G software installed (it sits in the task bar).

Do you have a Logitech keyboard as well?

No, just a mouse. The keyboard is from Microsoft.

So I downloaded the Steam version, and guess what, it produces the bug :)

So I got my video capture for a project I'm working on!

Now you've got me curious.

It's for a video about building a Windows XP gaming PC :)

I'm having this same issue, using a G303 mouse on Windows 10. Both the original FEAR on Steam as well as the platinum version on GoG.

Oddly enough, never had this issue with the same hardware on Windows 8.1.


EDIT:
I decided to watch a speedrun of FEAR since I couldn't actually play it myself due to this issue, and the speedrunner ran into the same bug. He was able to solve it temporarily by unplugging his mouse occasionally.

Meh. Same problem here. My solution: not worth the effort -.-

Is there some way GOG can fix this nonsense so that I don't have to turn my mouse and keyboard off to play? It was bad enough in the original FEAR, but now I'm lucky to get a little under 5 minutes before the framerate takes a nosedive.

I am also experiencing this slow down, from about 200 fps to 25. I followed the suggestions about the HID devices but it has made no difference.
All of the posts refer to the G series mouse and keyboard from Logitech. I have Logitech but the mouse is M310 and the keyboard is K520.

Replaced Logitech mouse and keyboard with Trust. No Logitech at all now. Slow down still happens, so it would appear not due entirely to Logitech. Possibly USB ?

Very possible, some HID devices may still trigger it, but not all can be disabled obviously. Also is not recommended to have too much USB ports connected before running game and avoid connect any new when game is running Weirdest stuff that happened to me was WIFI stopped responding or sound muted until reboot.