Download the free version of Malwarebytes and don't try the pro trial unless you wish to pay at a later date. Update it and run a full scan. Delete all it finds. Try a reboot to see if you can change your home page.
If that cures it download the free version of SuperAntiSpyware and update it and run a full scan to clear up cookies and any other missed bugs. Now you can now protect your homepage with SAS. Both these programs are very good and you will need to update them manually if you still wish to use the free versions. Worth keeping on the PC anyway.