Restart the computer in Safe mode or VGA mode.
Disable System Restore (Windows Me/XP).
Update the virus definitions.
Run a full system scan and delete all the files detected as Trojan.Dropper.
To turn off Windows XP System Restore
Click Start > Programs > Accessories > Windows Explorer
Right-click My Computer, and then click Properties.
Click the System Restore tab.
Check the "Turn off System Restore" or "Turn off System Restore on all drives" check box as shown in this illustration: