It is probably being called by one of your background running programs. And, whne you turn it off, it is just temporary until you restart and the background program starts again. Try turning it off as Iplural described, then try to individually stop your accessory background programs from starting up at boot. You can use msconfig for that. I see an ebay, messenger and a few others that maybe calling it. Once you find out which program is calling it, check the options for that program and you can probably find a place to stop it from calling that search bar. It is difficult to know exactly which program is calling it, because I can't really see all the programs you are running in the background, and I am not familar with all of those programs.
Another idea would be to do a search from that bar. If an ebay advertised banner pops up in the search then, you know that it is an Ebay option. Good Luck.