Where in registry did you look ?
Do you have rights to change registry entry ?
Does your computer logs in to a domain server?
have you tried a software called Spy Sweeper ?
http://downloads-zdnet.com.com/3000-2144-10200144.html
Ad-Aware WAS a good software a while back (some people may disagree with me) but it lost its touch and it does not do as good of job as other software like spy sweeper does.
in registry look under:
HKEY_CUrrent_User\software\Microsoft\Internet Explorer\Main
HKEY_LOCAL_MACHINE\software\Microsoft\Internet Explorer\Main
and change the Home page.
cheers