Time Warner quarantined my modem for downloading movies... help?

So, Time Warner Cable quarantined my modem for downloading movies. They said I have to reformat my computer. I deleted the movies with file deletion software, but I can't reformat my computer as I lost my windows disk a while back and can't afford $100 for another one. Is is sufficient to delete all of it like I did or do I really have to reformat? Anyone with a similar experience? Thanks.