unremovable lan setting automatic config script

i got a problem in my internet explorer,you see,in my IE’s LAN setting,witchs located in tools > internet options > connections > LAN setting,then there are 2 box that let’s you check,on the second one that says use automatic configure script, it has a box let’s you to fill it out,somehow this is what filled into the box:

http://localhost:9100/proxy.PAC

when i tried to remove it and click OK,go back there,it reappears again and when u try to place http://localhost:9100/proxy.PAC into the web address ,nothing shows up.i searched a few web sites about it and i don’t know if it’s the Google Web Accelerator that add the automatic script into there but one forum (http://forums.tomcoyote.org/index.php?showtopic=39090) says use hijackthis and remove the value:

it doesn’t show up in the select section in the hijackthis box.
it does indicated to be a spyware or shows up in spyware scans
does anyone has any idea how to remove this thingy of my computer?

Notice hijackthis can be download in download.com