Are you able to boot into Safe Mode with Networking?
Malicious Software Removal Tool will remove a rootkit
It will allow you to get deep inside of the operating system and see if it can spot the intruder.
Once it does, it will do all that it can to flush it out.
When your wallpaper loaded, could you see the start button?
Press Windows Flag key + R to open Run box
Type iexplore.exe
Press Ok
This launches an Internet Explorer window
If you can open an IE window and access the internet, run this free online scanner
http://housecall.trendmicro.com/
If you can only access Safe Mode Command Prompt Window
Type devmgmt.msc
Press Enter
It will open Device Manager
Look for yellow exclamation points or question marks
Right click on these drivers
Select Properties
You will see a message such as cannot load in safe mode or error code 23
Error code messages you may uninstall
I gave you this link earlier. Follow the suggestions and use TaskManager to open the Run box again. You can browse to these file locations and remove them if they are there.
See Kuttus Ram's Suggestion for removal:
These are manual instructions on removing FBI virus. Print them out so you can remove them the same way. Scroll down to bottom of the page for manual instructions
http://www.2-spyware.com/remove-fbi-virus.html
In Command prompt window type Regedit.exe
Press Enter
This opens Windows Registry
Look for the keys described in the manual removal instructions and delete them
Back up the registry first
http://windows.microsoft.com/en-US/windows7/Back-up-the-registry