|1] Easiest - Restore your computer to date previous the infection.|
2] There are settings in the registry that virus change when they hold your computer hostage. If you are unfamiliar with manually modifying the registry, get assistance from the local pro. If you search for the virus by exact name, there is usually information on what it changes and sometimes how to restore those settings.
3] In the long run, your time considered as valuable, it's better to format the disk and re-install Windows and get a better anti-virus running.
Make excellent back-ups!