Copyright Violation Virus

I recently got attacked by a virus that brings up the Copyright Violation pop up every time I start up. By all online accounts, this should be an easy fix, access task manager, end the processes, delete the files etc. Unfortunately, the virus seems to have disabled task manager, saying that the administrator has locked it. This means that all I get on start up is this pop-up, no start menu, toolbar etc etc, just the pop up which will not close, minimise or do anything. I try starting in safe mode, but I cannot access the administrator account, even though I have never changed the password. In safe mode the pop up still appears, and nothing else. I can't boot anything. It is very worrying. I have recovery console on my computer, but don't know if this is useful/ or how I would go about using it. I would run Malwarebytes, which usually does the trick for me, but again I can't boot or run any programs as the pop up prevents it. If I drag the pop up downwards, there is another pop up saying that I am infected and should buy my "unregistred Windows Defense" but I assume this is bogus as well, because I don't remember seeing it before, the graphics are shoddy, they want my money, and they misspell 'unregistred'. Please help, my computer is effectively useless!

 

I used the first link that you have provided, and found the instructions a little confusing, but after some trial and error, I managed to implement them successfully. I then ran Malwarebytes, which hopefully eradicated the viruses from my system. I faced some minor problems, such as not being able to run .exe programs afterwards, and having to change the admin password so as to access the 'unseen' system restore points, but after installing a couple of drivers and checking the web, I suspect that I hve resolved the issue. I am providing links in case of anyone else encountering this problem:

http://www.dougknox.com/xp/file_assoc.htm

http://www.kellys-korner-xp.com/win_xp_passwords.htm

Thanks for all your help, was really worried that the computer was stuffed. Eternal gratitude!!!