Why can't I close Bf3.exe

Did you install Battlefield 3 from another user account? You should probably reinstall the game. http://processhacker.sourceforge.net/index.php should be able to close programs there is causing trouble.

Also, you might want to try the following:

1. Open Task Manager. Go to the Process Tab.
2. Right click on the process and click on Properties.
3. Click on the Security Tab and then click on Edit.
4. On the Permissions window click on the Add button to open the Select Users Group or Groups window.
5. On the Select Users or Groups window you can enter the usernames of the accounts you want apply the restrictions.
6. Select your username and set the permissions to deny/allow by checking the checkbox under the deny/allow option.
7. Click on Apply and then Ok.

Please accept solutions if they are correct and press the XP button if somebody helped you. This way you help others in the same situation.

Cheers
-Carbonic