Portal 2

Whenever I change the sensitivity settings in the portal 2 config file and then enter the game, they change back to some default setting. Is there any way of avoiding this?

I changed the setting and then made it read only. When I close the game and go into the config file it has the right sensitivity permanently, but when I enter the game it definitely isn't the right sensitivity setting, even though the config file says so.

I have disabled mouse accell and set it to ignore windows sensitivity.

A reinstall will probably fix it

Go to your portal folder where the config file and create a new .cfg file named autoexec.cfg, then, in-game, open the console and type exec autoexec

It worked for me having the same problem with CS: GO