Default page at Internet Explorer

Dear Sir,
I have windows 2000 installed and internet explorer 5.0.
Whenever i open internet explorer it opens following page
http://tefs.com/passthrough/index.html?http://www.msn.com/

i made my default page as msn.com
i also tried blank pagebut it opens http://tefs.com/passthrough/index.html? and a seach broweser.
I deleted the address from registry too. but no solution wat to do ??
please help

Thanks