Assuming you`re on XP download Windows Defender click here and run it. Note that you will need to do a Full Scan which you`ll find by clicking the drop down arrow next to the Scan button.
If after a reboot the problem persists then the malware has put itself in the System Restore files and reloads on a reboot. Turn off system restore, repeat the scan, reboot and turn System Restore back on.
If it persists after that we`ll give you links to some other recommended software.