Click Start, Run, type regedit and press Enter. Be careful in Registry. Don't change anything if not sure.
On the left, for each of HKEY Local Machine, HKEY Current User, and HKEY Users:
expand each of them to ...\ Software\ Policies\ Microsoft
Expand further to see if you have ...\Internet Explorer \Control Panel
If so, highlight Control Panel, then look to the right and see if there is an item called "Homepage" (and the value is 1).
If you do find such a key, double click the item Homepage, and change it to 0.