There is a way to disable raw input.
The only thing you need to do is to right click on the file "portal.bat" click on edit and remove the " -noforcemaccel " and " -noforcemspd " from the file and replacing the last line ( "RInput\RInput.exe" hl2.exe ) with " del /A:H *.dat ".
That should enable Source Engine's mouse acceleration. (Don't copy the quotation marks.)
Thanks for the responses - In the .bat file I use it injects / tries to inject rinput voidedifbroken. Sorry if I didn't make it clear MagicSalad i'm trying to enable, not disable raw input. I load the portal.bat file which includes at the end - "RInput\RInput.exe" hl2.exe - however when Portal loads if I go into the mouse options there is no setting for raw input. The command m_rawinput if I enter it into the console also responds with Unknown command "m_rawinput."
Thanks
As I said, the batch file comes by default to inject the raw input in Source Unpack 2.4. However, if even with that you are sure that you do not have raw input enabled, you can manually inject it on manually. There is a folder on Source Unpack with a readme in it that ecplains it all.
Another important point is that in the version 5135 there is no option of enabling raw input from the menu.
An update has been released for SST that adds the command sst_portal_resetisg. This command removes Item Save Glitch and is to be used in place of restarting the game. This is a temporary solution while a more robust and legitimate one is developed.
The reasoning for allowing this is to make the ne