Why me :)
It does sound like it has been infected by something that is trying to block the normal ways of removing/killing it.
I personally use the kaspersky rescue disk and malwarebytes and find that between them they will remove most nasties. you can download them from the links at the bottom of the answer.
The kaspersky rescue disk needs to be burnt onto a CD using any burning software that supports burning ISOs, once the image has been burnt to CD you can boot the infected computer from it and then run a full scan (it will take a long time) and it should be able to find anything that would normally be locked/hidden by booting into windows.
for malwarebytes I'd suggest downloading it on another computer, putting it on a USB memory stick (or CD) and then boot the infected computer into safe mode with networking, install malwarebytes while in safe mode and then when it's installed run it, let it update (hence why you needed safe mode with networking) and then, again, run a full scan.
cont......