Download and install/update Spybot and Adaware and run a scan to find and delete all the Malwares.
Ad-Aware: http://www.lavasoftusa.com/software/adaware
Spybot: http://www.safer-networking.org/
Also, try the following manual registry settings:
1. Click Start - Run, type REGEDIT and press enter.
2. navigate to,
[HKEY_CURRENT_USER\Software\Policies\Microsoft\I nternet Explorer\Control Panel]
check if there is a DWORD called HomePage in the rightpane, if it is there right click the same and modify the value data to "0". If the DWORD is not available, right-click on the right pane [empty area] and click new then DWORD. Rename it as HomePage and set the value as "0"