Many time due to spywares or malwares you cannot change the Internet Explorer homepage. Even after running Anti-spyware like Spybot its not working. In such cases use the following trick to change it.

 In Regedit, navigate to this key:
HKEY_CURRENT_USER\Software\Policies\Microsoft\Internet Explorer\Control Panel
In the right-hand pane, right-click the “HomePage” value, then select Modify. Change it to: 00 00 00 00

Also change either or these to zero 0 instead of 1 if present:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer] – DWORD “NoSetHomePage”=dword:00000001

[HKEY_CURRENT_USER\Software\Policies\Microsoft\Internet Explorer\Restrictions] – DWORD “NoSetHomePage”=dword:00000001

If you don’t have this key, browse to:
HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main

and in the right hand pane, double click “Local Page” and set equal to “C:\WINDOWS\System\blank.htm” (no quotes) which will hopefully set your Home Page to blank and then allow you to subsequently modify it using Internet Options.

I’m sure this will solve the problem.

Warning:
Editing Registry may cause OS failure. Edit registry only when you are sure of it. Make a backup of registry before editing.