can u use regedit?
In your Windows Start the regedit program. (Click Start > Run > Enter "Regedit.exe")
Check the following registry settings:
[HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain]
"Start Page"="http://www.yahoo.com"
[HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerMain]
"Start Page"="http://www.yahoo.com"