Trojan.Delf.Inject.BK:

This is a Trojan program that was found in July 2009. A simple piece of code that doesn't do much damage alone. But, its good at what it was made for. As far as the experiments made on this one, it's major aim is just to download malicious files to your computer. It may also ping to several ports and can steal your passwords if updated. It creates a few registry entries in order to launch itself on startup. As soon as the Internet is connected, it pings to servers to download the other viruses. If not removed immediately, this Trojan-downloader may create a lot of damage to your system by downloading other worms.

Manual instructions to remove Trojan.Delf.Inject.BK:

1. Disable your System restore (to learn how to, click here) and reboot your system in the safe mode.
2. Lets begin with deleting the registry keys created by the Trojan. Go to Start-->Run and type "regedit". Navigate to the following registry items
   
   [HKLM\Software\Microsoft\Windows\CurrentVersion\Run]\MicrosoftNAPC
[HKLM\Software\Microsoft\Windows\CurrentVersion\policies\Explorer\Run]\MicrosoftCorp
   
   Look for the path with the name "Tray.exe" as the filename and delete the whole path. For example, if it is "%system%\tray.exe", delete only that path.


3. But just to be sure, use the Ctrl+F and find the entry having the string "tray.exe" in the registry. You'll most probably not find any entries but still just to be sure, it is best to search for it so that you can be satisfied that the virus has been completely deleted.
4. Now restart your system again in the Safe mode and delete the file "C:\WINDOWS\System\tray.exe". Check the Task manager and go to the Processes tab to see if any process with the name "tray.exe" is running. If you find any, end it immediately.
5. Once you delete the file, you can enable your System restore again and relax. You're free from this Trojan.