Here is some infomation on the file:http://www.bleepingcomputer.com/startups/wpa.exe-11886.html
Have you tried running AVG in safe mode? You will get a better success rate there. You can boot into safe mode by pressing the F8
key right when Windows starts, usually right after you hear your computer
beep when you reboot it (some versions of windows will display 'Starting Windows' with a grey progress bar)
you will be brought to a menu where you can choose to boot into safe mode. If it does not work on the first try, reboot and try again, as you have to be quick when you press it.