Backup your data.
Assuming it's XP but would probably work with Vista and maybe 7.
Download Malwarebytes on another PC and copy the download to a memory stick.
On the infected PC turn off System Restore and reboot. If it won't accept F8 to boot into safe mode it may be due to a wireless keyboard. Connect an old fashioned one and it may work.
Once in safe mode, log in, connect memory stick and install Malwarebytes. Allow to update and run a full scan. Let it do the business and reboot.
Run another full scan and if all is well turn System Restore back on.
Hope that helps and works for you. To prevent future occurrence ditch Windoze and install Linux.