not a virus. Try Grif's method of removing malware
here > http://forums.cnet.com/7726-6122_102-5509131.html?tag=posts;msg5553967
istart123 mysteriously took over the home page of all 3 of my web browsers. You can't close it. It takes over your start page. You can't get rid of it. If you close it's tab, it simply pops another tab back up. It is not a registered program, and there is no program that you can uninstall. I attempted to find istart123 in the Windows 7 registry, but though the name comes up, I was unable to find associated files to delete. Has anyone had this problem?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic