There are some free programs providing registry optimizations and those things and some of them changes the homepage and even if you reset the homepage it will go back to the unwanted website.
The solution can be uninstalling such software if you have installed.
Another thing is that there are ActiveX and VB softwares installed from your browser when you were surfing some idiotic sites. Most of them get to you with popup windows.
And it will force you to click "Yes" granting them the permission to install their software.
Once you click "yes", you are giving them everything you can possibly give and you remain bare naked.
They can install something to your pc and hide somewhere that is difficult to find.
Yes, most of them are hidden in the registry and some of them will automatically load stealthly during your windows bootup. This can be avoided by increasing your security level from your browser opton to prevent those unwanted program from running from your browser.
I suggest is that you search those programs.
Some can be found at your \ProgramFiles\??? and you might find that it has an uninstaller.
Or, you might find it in the add/remove software in your control panel.
you might want to run msconfig and see in the startup list and if you find some suspicious programs, delete them.
And finally, run the registry cleanup software and remove related registries.
Reboot and see if it works.
If it doesn't work, the final solution will be a clean install of your windows. - Don't reinstall over your old windows!!!
If you have only 1 partition and don't want to format your windows, then you can
1. rename the win.com file to win.xxx
2. rename the Windows folder to win.xxx
3. rename the Program Files folder to prog.xxx
4. reboot and install from CD.
If this is not helpful, you can give me that PC for free.
Yours is mine... and mine is mine....