REBOOT your computer into SafeMode, perform a full scan with the antivirus and delete the backdoor.Starting your computer in Safe mode
, use the F8 method.
If you can not remove the backdoor download HijackThis
, unzip the file into a folder, e.g. c:\HJT, open HijackThis.exe, press "Scan", and "Save Log". Copy and paste the WHOLE contents of the log in this thread. Don't fix anything yet.
ZoneAlarm Free is a good firewall for beginners:Download ZA Free