You don't have to reinstall the operating system, if that's the same virus that I think it is. Open up task manager and try and find a process running that's named just "a". No quotation marks, just a lowercase a all by itself running. If it is there, END IT and post back and I'll see if I can help further. If that's not it, then I don't know, lol
EDIT: and LOL at how it wants to "pervent" data loss. It's 'prevent' lmao